HK1081655A - Synchronizing timing between multiple air link standard signals operating within a communications terminal - Google Patents

Description

Synchronous timing between multiple airlink standard signal operations in a communication terminal

Background

I. Field of the invention

The present invention relates generally to wireless communication networks. More particularly, the present invention relates to a method and apparatus for synchronizing timing in circuitry associated with a wireless communication terminal supporting multiple airlinks or multi-mode phones.

Related Art

There are many different types of wireless telephone or wireless communication systems, including different land-based wireless communication systems and various satellite-based wireless communication systems. Different land-based wireless communication systems may include personalized communication services as well as cellular systems. Examples of known cellular systems include the cellular analog Advanced Mobile Phone System (AMPS), and the following digital cellular systems: code division multiple access system (CDMA); time division multiple access systems (TDMA); and newer hybrid digital communication systems that use both TDMA and CDMA technologies.

The use of CDMA techniques in Multiple Access Communication systems is disclosed in U.S. patent No. 4,901,307, entitled "Spread Spectrum Multiple Access Communication System Using satellite Terrestrial repeats," and U.S. patent No. 5,103,459, entitled: U.S. Pat. No. 5 System And Method for generating Signal waves In A CDMA cellular telephone System, which is assigned to the assignee of the present invention And is incorporated herein by reference.

The method for providing CDMA Mobile communications IS standardized by the telecommunication industry Association in the United states under the heading "Mobile Station-Base Station compatibility Standard for Dual-Mode Wireless band Spread Spectrum Cellular System", referred to herein as IS-95, by TIA/EIZ/IS-95-A. A combined AMPS & CDMA system IS described in TIA/EIA standard IS-98. Other communication systems are described in IMT-2000/UM, or International Mobile Telecommunications System 2000/Universal Mobile Telecommunications System, the standard of which covers the standards known as WCDMA, CDMA2000 (e.g., CDMA2000Ix or 3x standard) or TD-SCDMA.

In the above-mentioned patent, CDMA technology is disclosed in which a large number of mobile station users, each having a transceiver, communicate via satellite relays or terrestrial base stations. The satellite relays are referred to as gateways and the terrestrial base stations are referred to as cell-sites. The gateway provides a communication link for connecting a user terminal to other user terminals or users of other communication systems, such as a public switched telephone network. By using CDMA communications, the spectrum may be used by multiple terminals, thereby permitting an increase in the capacity of a system user. The use of CDMA techniques results in higher spectral efficiency than can be achieved using other multiple access techniques.

In a typical CDMA communication system, both the remote unit and the base station use modulation and demodulation of transmitted data with high frequency pseudo-noise codes (PN) or with orthogonal walsh codes, or both, to identify simultaneously received signals from the other. For example, in the forward link, base station to mobile station direction, IS-95 separates transmissions from the same base station for different users into different channels by using different walsh codes for each transmission, while transmissions from different base stations are distinguished using a unique offset PN code. In the reverse link, i.e., mobile to base station direction, different PN sequences are used to distinguish different channels or user terminals.

The forward CDMA link includes a pilot channel, a synchronization (sync) channel, one or more paging channels, and a number of traffic channels. The reverse link includes an access channel and a number of traffic channels. The pilot channel transmits a beacon signal, referred to as a pilot signal, and is used to alert the mobile station to the presence of a CDMA compliant base station. After a mobile station has successfully requested a pilot signal, it can then receive and demodulate the synchronization channel to obtain frame-level synchronization, system time, and so on. The synchronization channel carries a repeated message that specifically identifies the base station to provide system level timing and to provide the absolute phase of the pilot signal. This feature will be discussed in more detail below. The paging channel is used by the base station to allocate communication channels and communicate with the mobile station when the paging channel is not allocated to a traffic channel. Finally, the traffic channels assigned to individual mobile stations are used to carry traffic such as voice and data.

In order to properly communicate in a CDMA system, the state of the particular code selected must be synchronized at the base station and the mobile station. When the state of the coding at the mobile station system coincides with the coding state within the base station, coding level synchronization is achieved, except for some offset to account for processing and transmission delays. In IS-95, this synchronization IS facilitated by the transmission of a pilot signal, which comprises a repeated transmission of a uniquely offset PN code (pilot PN code) from each base station. In addition to facilitating synchronization at the pilot PN code level, the pilot allows each base station to be identified relative to the other base stations surrounding it using the pilot channel phase offset. Thus, the pilot channel provides the mobile station with a first level of access to timing information for the detailed PN sequence.

The mobile station initiates a request for an IS-95 based communication system by searching for a valid pilot signal within a definable search window. Pilot signals associated with different base stations are distinguished from each other based on the phase (time offset) of the pilot signals. Thus, although each base station transmits a uniform pilot signal, the pilot signals from different base stations have different phases. A 9-bit number can be used to identify the pilot phase and is referred to as the pilot offset.

After a mobile phone requests a valid pilot signal and correlates the pilot signal with a particular base station, the mobile station can receive and demodulate the synchronization channel. In addition to providing the mobile station with the phase of the pilot signal and the identity of the base station with which it is associated, the synchronization message also includes CDMA system level timing information. Although system time may be provided by several different timing sources, conventional wireless communication systems derive system timing information by a global positioning system satellite system located at each base station.

In light of the convenience and availability of some mobile phones, the Federal Communications Commission (FCC) now requires Wireless Communications System (WCS) providers in the united states to implement a mechanism to automatically route 911 calls to the nearest emergency services processing center. This is called the E911 requirement. To accommodate this requirement, the WCS must be able to quickly and accurately determine the geographic location of a mobile phone or wireless device. Conventional wireless communication systems typically use what is referred to as a handset-based solution or a network-based solution to determine the location of a user or mobile station.

Traditionally used handset-based methods typically rely on GPS capability to provide user location information. However, such GPS solutions exhibit reduced performance and capabilities in areas where satellite coverage is limited or obscured, such as in the home or in major urban areas. GPS solutions also provide a position determination relatively slowly and can be expensive. Network-based solutions rely on a signal transmitted from a mobile station to a plurality of fixed base stations. However, the limitation here is that multiple base stations are required. Thus, providing location information using a network-based solution would be problematic if a user is in an area with limited base station coverage.

Another problem considered with GPS-based solutions is that a GPS acquisition device may have a significant amount of search space, including different codes, timing, etc., to search. The size of the timing window for the different timing hypotheses that need to be tested to obtain the GPS signal may be very large. This requires more time than desired to acquire signal timing or to implement the GPS measurements, and also affects the accuracy of the measurements.

Thus, there is a need for a system and method that eliminates the disadvantages of the conventionally used positioning techniques. More particularly, what is needed is a system and method for implementing a multimode dual circuit or ASIC wireless device that can share precise time among multiple ASICs. Sharing system time in the signal processing circuits speeds up the process of position determination and facilitates the broadcasting of system time throughout the WCS network. Also, what is needed is a multi-mode phone that is constructed and arranged to facilitate sharing of WCS system time between ASICs within the same mobile phone. A system and method constructed and arranged in this manner can accommodate both the GPS solutions and network-based solutions discussed above and provide timely and accurate handoff for supporting E911 features and/or timely interconnected systems, such as: position data from CDMA to wideband CDMA (W-CDMA).

Summary of The Invention

Example embodiments include an apparatus and method that uses a first communication device having at least first and second types of communication paths adapted to receive first and second timing signals over the first type of communication path and to transmit data over the second type of communication path. The transmitted data is associated with the received first timing signal. In some embodiments, the first type of communication path includes a forward link and the second type of communication path includes a reverse link. The first and second timing signals may comprise pilot and synchronization channel message signals, respectively.

A processor is coupled to the first communication device and configured to receive a second timing signal and generate a timing word. The timing word may include, for example, information related to adjustments to compensate for path delays. A second communication device having at least a first type of communication path is coupled to the processor and adapted to receive the timing word and the transmitted data and derive synchronization information. The generated derived synchronization information is correlated with the first timing signal, and the processor performs one or more operations in accordance with the received second timing signal and the derived synchronization information. The performed operations include deriving timing information associated with the second communication device. Alternatively, the operations include obtaining one or more communication signals in accordance with the received second timing signal and the derived synchronization information. In some embodiments, the one or more communication signals include at least one timing signal associated with a positioning satellite network.

In an example embodiment, the first and second communication devices include first and second application specific integrated circuits.

The apparatus may further include a tuner coupled to the processor to receive a plurality of radio frequency signals based on a first processor control signal and to generate a selected frequency signal as an output. A first switch coupled to the processor receives a second processor control signal and the selected frequency signal from the tuner and selectively switches the selected frequency signal between two or more outputs.

In this embodiment, a first circuit is coupled to the processor, the tuner, and the first switch and includes a first receive path that may be coupled as a forward communication link to a first switch output port to receive the selected frequency signal. The selected frequency signal includes a timing component of a first type and a sync word that is output to the processor, which generates a timing component of a second type in response. The timing component may include, for example, pseudorandom noise level timing information. A time tracking device is configured to receive the first and second timing components, to perform a first synchronization operation in response, and to generate a synchronization point in accordance with the first synchronization operation. An encoding generator coupled to the processor receives the communication message from the processor and generates and provides a data sequence to the time tracking device, which generates an associated data sequence based on the synchronization point and the communication message. The first transmit path, which may be a reverse communication link, is configured to receive the correlated data sequence and generate a synchronized data stream and transmit the synchronized data stream using the first transmit path output port.

A second switch is electrically coupled to the processor and the first transmit path output port, has two or more second switch output ports, and is configured to receive a third processor control signal and the synchronous data stream and to selectively switch the received synchronous data stream between the two or more second switch output ports. A third switch includes two third switch input ports and an output port, having a first input port coupled to the second output port of the first switch, and a second switch input port coupled to one of the second switch output ports. The third switch is configured to receive a fourth processor control signal, receive the selected frequency signal using a first third switch input port, and receive the synchronized data stream using a second third switch input port.

In this embodiment, a second circuit is also coupled to the processor and the third switch includes a second receive path, which may be a forward communication link, having an input port coupled to the output port of the third switch to receive a selected one of the synchronized data stream and the selected frequency signal, and a correlator coupled to an output of the second receive path and configured to detect the presence of the synchronized data stream upon reception and provide the synchronized data stream as an output. A time measurement mechanism having an input coupled to an output of the correlator and another input coupled to the processor for receiving the synchronization data stream from the correlator and the synchronization word from the processor and deriving a timing window therefrom.

A method for obtaining a timing signal includes receiving first and second timing signals, such as a pilot signal and a synchronization channel message, on a first communication path of a first communication device, and transmitting data on a second type of communication path of the first communication device, the transmitted data being associated with the received first timing signal. The first type of communication path may be, for example, a forward communication link and the second type of communication path may be a reverse link. The second timing signal is received in the processor and converted into a word. The transmitted data, the derived synchronization information, and the timing word are received in the second communication device, and one or more operations are performed in accordance with the received transmitted data and the timing word.

Another embodiment includes a communication device configured to operate in first and second airlink modes, such as: those satellite, CDMA, W-CDMA, and GSM-based wireless communication systems have at least first and second types of communication paths adapted to facilitate communications at least during a first air link mode. The communication device is configured to receive first and second timing signals over a first type of communication path, the first and second timing signal data representing first and second timing signals, respectively, stored in a memory of the communication device, and to transmit communication data over a second type of communication path, the communication data being transmitted in accordance with the first timing signal data. The second airlink mode includes at least a first type communication path configured to facilitate communication with the communication device during operation of the second airlink mode and configured to receive the transmitted communication data and generate therefrom first type synchronization information. A timing mechanism is configured to be activated during the second airlink mode and to receive the first type of synchronization information, and a processor coupled to the communications device is configured to receive the second timing signal data stored in the memory and to generate therefrom the second type of synchronization information which is provided to the timing mechanism during activation.

Features and advantages of the present invention include the ability to provide a multi-mode dual chip phone for performing fast GPS measurements in E911 support. Sharing WCS system time is not only applicable between multiple processing circuits or ASICs but also in a single reconfigurable multi-mode ASIC. Sharing WCS system time among multiple ASICs and among a single reconfigurable ASICs allows for more rapid and accurate acquisition of GPS and other types of services. Finally, the sharing of WCS system time minimizes the frequency of dropped calls due to the mobile phone performing GPS measurements.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages, and principles of the invention. In the drawings:

FIG. 1 illustrates an example wireless communication system;

FIG. 2 illustrates an exemplary illumination range having a plurality of beams;

FIG. 3 illustrates an example mobile communication terminal;

FIG. 4 is a block diagram showing an ASIC configured for different airlink standards;

FIG. 5 is a more detailed block diagram of the ASIC presented in FIG. 4

FIG. 6 is a block diagram of a single ASIC configured to operate in accordance with embodiments of the present invention; and

FIG. 7 is an exemplary method of implementing an embodiment of the present invention.

Detailed description of the invention

The following detailed description of the invention refers to the accompanying drawings that illustrate exemplary embodiments consistent with this invention. Other embodiments are possible and modifications may be made to the embodiments within the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense. Furthermore, the scope of the invention is defined by the appended claims.

As will become apparent to those of ordinary skill in the art, the embodiments may be implemented in various different embodiments of hardware, software, firmware, and/or the entities depicted in the figures. Any actual software code with the specialized controlled hardware to implement the present invention is not limiting of the present invention. Thus, the operation of the present invention and the behavior thereof will be described with the understanding that modifications and variations of the embodiments are possible, given the level of detail presented herein.

Before describing the present invention in detail, it is helpful to describe the environment in which they will be implemented. Embodiments of the present invention are particularly useful in a mobile communications environment. Fig. 1 depicts such an environment.

Fig. 1 is a block diagram of an exemplary Wireless Communications System (WCS)100 that includes a base station 112, 2 satellites 116a and 116b, and two associated gateways (also referred to herein as hubs) 120a and 120 b. These elements engage in wireless communications with user terminals 124a, 124b, and 124 c. Typically, the base stations and satellites/gateways are components of different land-based and satellite-based communication systems. However, these various systems may interoperate as an overall communication infrastructure.

The base station 112 may form part of a land-based communication system and network that includes multiple PCS/cellular communication cell terminals. The base station 112 may be associated with a land-based CDMA or TDMA (or hybrid CDMA/TDMA) digital communication system to transmit or receive terrestrial CDMA or TDMA signals to or from a mobile user terminal. The terrestrial signals may be formatted in accordance with the IMT-2000/UMT standard (i.e., international mobile telecommunications system 2000/universal mobile telecommunications system standard). The terrestrial signal may be a wideband CDMA signal (referred to as a WCDMA signal), or a CDMA2000 compliant standard (e.g., CDMA 20001 x or 3x standard), or a TD-SCDMA signal. Alternatively, the base station 112 may be associated with an analog terrestrial based communication system (e.g., AMPS) that transmits and receives analog communication signals.

Although fig. 1 depicts one signal base station 112, two satellites 116, and two gateways 120, other numbers of these elements may be used to achieve a desired communication capacity and geographic scope. For example, an example implementation of WCS100 includes 48 or more satellites operating in a plane of 8 different orbits in Low Earth Orbit (LEO) to serve a large number of user terminals 124.

The terms base station and gateway are sometimes used interchangeably, each being a fixed central communication station, and are perceived in the industry as highly specialized base stations for gateways, such as gateway 120, which are known as base stations (also sometimes referred to as cell sites), such as: the base stations 112, when communicating directly within the surrounding geographic area using terrestrial antennas, communicate directly through satellite repeaters.

Each of the user terminals 124 has or includes an apparatus or wireless communication device such as, but not limited to, a cellular telephone, a wireless handset, a data transceiver, or a paging or position location receiver. Still further, each user terminal 124 may be hand-held, portable mounted on a vehicle (including cars, trucks, boats, trains, and planes), or stationary, as desired. For example, fig. 1 illustrates user terminal 124a as a fixed telephone, user terminal 124b as a handheld portable device, and user terminal 124c as a vehicle-mounted device. Wireless communication devices are also sometimes referred to as user terminal mobile stations, mobile units, subscriber units, mobile radios or radiotelephones. Wireless units, or simply preferences in some communication systems, are referred to as "users" and "mobile devices".

User terminals 124 engage in wireless communications with other components in WCS100 via a CDMA communications system. Moreover, the present invention may be used in systems using other communication techniques, such as Time Division Multiple Access (TDMA), and Frequency Division Multiple Access (FDMA) or other waveforms or techniques listed above (WCDMA, CDMA2000 … …).

Typically, from a beam source, for example: beams of base stations 112, or satellites 116, cover different geographic areas in a predefined pattern. Waves of different frequencies, also referred to as CDM channels or "sub-beams," may be indicated for covering the same area. Those skilled in the art will also readily appreciate that beam coverage or service areas for multiple satellites, or antenna patterns for multiple base stations, may be designed to overlap, either completely or partially, in a given area, depending on the communication system design and the type of service being provided and whether spatial diversity is implemented.

Fig. 1 illustrates several exemplary signal paths. For example, communication links 130a-c provide for the exchange of signals between base station 112 and user terminals 124. Similarly, communication links 138a-d provide for the exchange of signals between satellites 116 and user terminals 124. Communications between the satellites 116 and the gateways 120 are facilitated by links 146 a-d.

User terminals 124 are capable of engaging in two-way communications with base station 112 and/or satellites 116. Thus, communication links 130 and 138 each include a forward link and a reverse link. A forward link conveys information signals to user terminals 124. For terrestrial based communications within WCS100, a forward link conveys information from base station 112 to a user terminal 124 over a link 130. A satellite-based forward link in the context of WCS100 conveys information from gateway 120 to satellite 116 via a link 146 and from satellite 116 to user terminal 124 via a link 138. Thus, a land-based forward link typically includes a single wireless signal path, while a satellite-based forward link typically includes two paths or links.

In the context of WCS100, a reverse link conveys information signals from a user terminal 124 to one of base stations 112 or gateways 120. Similar to the forward link in WCS100, the reverse link typically requires a single wireless connection for terrestrial-based communications and two wireless connections for satellite-based communications. WCS100 may provide communication of different characteristics between these forward links, such as Low Data Rate (LDR) and High Data Rate (HDR) services. An example LCD service provides data rates from 3Kbits/sec. (Kbps) to 9.6Kbps, while an example HDR service supports data rates of 604Kbps or higher.

HDR services may be bursty in nature. That is, communication over the HDR link may begin abruptly and end in an unpredictable manner. Thus, in one example, an HDR link may operate at 0Kbps while at a very high data rate at the next time instance, such as: 604kbps operation

As described above, WCS100 performs wireless communications in accordance with CDMA techniques. Thus, the signals transmitted over the forward and reverse links of links 130, 138 and 146 are encoded, spread and channelized according to the CDMA transmission standard. In addition, block interleaving may be used between these forward and reverse links. The blocks are transmitted in frames having a predetermined duration, e.g., 20 milliseconds.

Base stations 112, satellites 116, and gateways 120 may adjust the energy of their signals transmitted over the forward links of WCS 100. This energy, referred to herein as forward link transmit energy, may vary over time in response to signals, requests or instructions received from user terminals 124. This time-varying feature may be used on a frame-to-frame basis. The power adjustment is performed to maintain the forward link Bit Error Rate (BER) within certain requirements, reduce interference and conserve transmission energy.

For example: gateway 120a may transmit signals to user terminal 124b via satellite 116a with different forward link transmission energy than for user terminal 124 c. In addition, gateway 120a may vary the transmit power of each forward link to user terminals 124b and 124c for each successive frame.

Fig. 2 depicts an example satellite beam pattern 202, also referred to as a footprint. As shown in fig. 2, an exemplary satellite footprint 202 includes 16 beams: 204₁-204₁₆. Each beam covers a particular geographic area, although some beams often overlap. The satellite footprint shown in FIG. 2 includes an inner beam (beam 204)₁) Intermediate beam (beam 204)₂-204₇) And an outer beam (beam 204)₈-204₁₆). The beam pattern 202 is a configuration of a particular set of predetermined gain patterns, each of which is associated with a particular beam 204.

For illustrative purposes only, beams 204 are depicted as having a non-overlapping geometric shape. In practice, each beam 204 has a gain pattern profile that is well beyond the ideal boundaries shown in fig. 2. However, these gain patterns may be attenuated when the illustrated boundaries are exceeded, and thus they typically do not provide significant gain to support communications with user terminals 124 outside of a given "boundary".

Each beam 204 may be considered to have a different region based on the proximity of the beam to other beams and/or the location of the beam within the gain pattern of the other beams. For example, FIG. 2 shows beam 204₂Having a central region 206 and an intersection region 208. Crossover region 208 includes beam 204₂With the beam 204₁、204₃、204₇、204₈、204₉And 204₁₀Of the adjacent abutment region. Due to this proximity, user terminals 124 within crossover region 208 (which are the same as similar regions within other beams) are more easily switched to adjacent beams than user terminals 124 within center region 206. However, in areas where handover is possible, for example: user terminals 124 in crossover region 208 are also more susceptible to interference from communication links in adjacent beams 204.

Fig. 3 is a more detailed illustration of an exemplary mobile phone 124b used in the present invention. As described above, the mobile phone 124b is a multi-mode or multi-band mobile phone that can operate in accordance with a plurality of wireless communication standards. Although the present application focuses primarily on CDMA-IS 95 and LEO satellite communications applications, it IS not limited to these standards. Many other air link standards may also be suitable, such as wideband CDMA (W-CDMA), Global System for Mobile communications (GSM), or other suitable wireless communication standards.

The exemplary mobile phone 124b shown in FIG. 3 includes an antenna 306 for Radio Frequency (RF) operation compatible with the airlink standard of WCS 100. The exemplary mobile phone 124b includes several mode selection switches 302, 304, and 305 that are used to select between different air link standards compatible with the phone 124b and the WCS 100. Finally, the example mobile phone 124b may include other standard features, such as: speaker 308, display panel 310, keypad 312, and microphone 314. Mode select switch 302 is used to select, for example, a terrestrial airlink communication mode and mode select switch 304 is used to select a satellite airlink communication mode. The mode select switch 305 is used to activate an E911 emergency response mode.

However, those skilled in the art will readily appreciate that embodiments of the present invention are not limited to these manually operated mode selections or emergency response activations. The selection is typically as a result of a manual device user input, wherein a switch or combination of one or more buttons on the wireless device is used to select a particular mode. Alternatively, processing of pre-selected or pre-stored commands or method steps that may result in the selection of a mode based on a particular value, parameter, or criteria change may be used to trigger a mode selection circuit or switch. For example: detection of a collision or injury to the wireless device, indication of injury to the user, detection of excessive gravity (spontaneous event), ambient conditions of the wireless device, similar to a significant change in temperature (exposure), may be used in some wireless devices to activate a mechanism such as an emergency request, or request activation. Various types of sounds or signal-activated components of audio or programs may also be used as desired.

As explained above, in the united states, the FCC requires that mobile phone service providers be able to identify all of the mobile phones in use, for example: the 911 call from the mobile phone 124b provides location information with predetermined parameters. To meet the requirements of providing location information for E911 services, WCS100 utilizes information provided in part by LEO satellites 116a and 116 b. The mobile phone 124b is capable of multi-mode functionality that is required to process information from both LEO satellites and GPS satellites using various signal processing circuits or functional circuit components, controllers, or modules, such as receivers/transmitters, correlators, and modulators/demodulators. Although a single software reconfigurable Application Specific Integrated Circuit (ASIC), Software Defined Radio (SDR), or Field Programmable Gate Array (FPGA) type radio may be used, fig. 4 illustrates an embodiment using two different ASICs to accommodate the two different airlink standards selected by mode switches 302 and 304. A wireless device may use two or more ASICS or sets of circuits or devices, each dedicated to performing a specific task.

Fig. 4 is a block diagram 400 of an exemplary ASIC configuration for use in the mobile phone 124 b. In fig. 4, a first ASIC402 is used to implement terrestrial air link communications selected by the mode switch 302. The ASIC402 supports a forward link channel 405 and a reverse link channel 406. The forward link is adapted for mobile telephone traffic as previously described. Forward link traffic is initiated at a serving base station, e.g., base station 112, and transmitted to a receiving user's terminal/wireless device, e.g., mobile station 124 b. Similarly, the reverse link 406 is used to carry traffic in the direction from the mobile phone to the base station. The reverse link 406 also includes a switch 408 that transmits reverse link information from the ASIC402 to other portions of the mobile phone 124b for transmission.

The second ASIC404 is provided to accommodate, for example, the satellite communication mode selected by the mode switch 304 of the mobile phone 124 b. The second ASIC404 also includes a forward link 412 and a reverse link 414. The forward link 412 includes a switch 416 for receiving timing data 418 forwarded from the reverse link 406 of the first ASIC 402. The switch 408 is used as a conduit to inject, insert, or add timing data 418 directly to the forward link 412 of the second ASIC404 through the switch 416. The injection of timing data 408 from the first ASIC402 provides the most accurate system timing information to the second ASIC404, thus allowing the second ASIC404 to reduce the time required to obtain its own individual timing information associated with the new air-line standard on the forward link 412 when the switch 416 is set to allow acquisition of a new signal and the size of a search hypothesis

The need for separate timing information is critical, for example, when a user of a mobile phone 124b or a communication system or other element uses the mode select switch 305 to activate the E911 feature while communication is using the LEO mode selected by the mode select switch 304. By receiving system timing information from the ASIC402, the ASIC404 can reduce time and increase the accuracy with which GPS measurements are performed. In other words, the present invention synchronizes the first ASIC402 and the second ASIC404 to the same system reference time.

As is known in the art, the system reference time is typically derived from a "universal time" source, such as, but not limited to, GPS, and is used to synchronize component components and operations of a communication system, such as WCS 100. The technique of this embodiment is advantageous in that it has a higher timing accuracy than can be provided using other techniques, such as an interrupted handshake method. That is, using conventional techniques, the second ASIC404 needs to first acquire the air-line and then derive the timing information completely from the air-line signal received on the forward link 412, without being able to utilize any previous timing information. The received air link signal is provided when the forward link 412 is switched from an RF source associated with the first ASIC402 to an RF source associated with the second ASIC 404.

These conventional techniques require a relatively significant overhead time to acquire, receive, demodulate, and identify the forward link pilot signal. More time is required to demodulate an assured synchronization channel message and then extract the correct timing information. However, the technique of the present embodiment eliminates the overhead time required to perform these additional processing steps. Although other techniques may be used to guess the timing associated with the second ASIC402, such guessing may not provide the necessary to perform GPS acquisition and measurements as implemented by embodiments of the present invention, for example. The operation of this embodiment will be described in more detail below.

A user activates the E911 feature by actuating the mode switch 305 of the mobile phone 124B. Thus, the first ASIC402 will demodulate the forward link signal 405 on the established 911 voice call. At the same time, however, the second ASIC404 must make GPS measurements to provide location information in support of the E911 emergency response mode. To quickly and accurately perform such measurements, the second ASIC404 must synchronize itself with the LEO system time, which may include, for example, CDMA system time. The second ASIC404, however, cannot demodulate the LEO signal associated with the first ASIC402 because the forward link signal 405 is at a different RF frequency, as explained above. The timing data must be transferred from the first ASIC402 to the second ASIC404 by essentially hijacking a signal from the reverse link 406 of the first ASIC 402.

The first ASIC402 is programmable, for example, to transmit CDMA forward link PN sequences using a long-code mask of zero, commonly referred to as a zero. To assist in this process, a switch 408 is provided to switch the reverse link 406 away from the first ASIC402 and into the forward link 412 of the second ASIC 404. This can be done at the digital baseband frequency of the signal or after the signal has been converted to analog form. The second ASIC404 can then search for and obtain what is considered a true forward link pilot signal, which is in effect a hijacking signal 418 from the reverse link 406 of the first ASIC 402.

The second ASIC404 then synchronizes its own time with the PN code change (at the beginning of the restart) or the roll over of the timing data signal 418. Given the known hardware delays, the second ASIC404 now knows the CDMA system time, equal to about 26.6 milliseconds, within a system frame period, and also meets the desired resolution. This process allows the first and second ASICs402 and 404 to exchange precise timing information whenever they share the same PN sequence. A more detailed illustration of the processing system 400 is shown in fig. 5 and discussed below.

In fig. 5, the processing system 400 includes a processor, microprocessor or controller 502, generally programmable, that includes first and second input ports 520a and 502b, and an input port 502 c. The microprocessor 502 controls the operation of the system 400 by providing control signals from the output ports 502a and 502b to synchronize the operation between the first and second ASICS402 and 404. As shown, the microprocessor 502 is connected to the first and second ASICs402 and 404, the tuner 503, the switch 504, and the switches 408 and 416 also shown in fig. 4. Although mobile phone 124b is compatible with two or more air-link standards, it typically uses a single RF signal front-end component.

Tuner 503 scans the RF spectrum for signals that meet the air link standard selected by the user. I.e., tuner 503 may tune to a particular frequency to receive a desired RF signal from the plurality of RF signals 507 a. The tuner selects a desired RF signal 507b based on a control signal received from the output port 502a of the processor 502a and provides the desired RF signal 507b to the switch 504. The switch 504 may be implemented using any number of suitable switching devices, such as a relay or a transistor, and in the exemplary embodiment of fig. 5, the switch 504 selectively switches the desired RF signal 507b in accordance with a control signal. Based on the received control signal, the switch 504 provides the desired RF signal 507b to one of the output ports 505 or 506.

In the example processing system 400 of fig. 5, if the user actuates the land-based mode selection switch 302 of the mobile phone 124b, the ASIC402 is activated when a signal 507b is provided to the output port 506 of the switch 504. On the other hand, if the user actuates the satellite mode select switch 304, the desired signal 507b is provided to the output port 505 of the switch 504 and then to the switch 416.

As explained above, the first ASIC402 in the example processing system 400 is used to accommodate land-based communication modes. Although the ASIC402 includes several components required for receiving and processing a terrestrial signal, only those components of the ASIC402 that are particularly relevant to this embodiment are shown in fig. 5.

The ASIC402 includes a receive path 508. The receive path 508, which includes known components (not shown), such as a receiver, an Automatic Gain Control (AGC) module, and a correlator, is used as a front end for the ASIC 402. A receive path input port 508a receives the selected frequency signal 507b forwarded using the switch 504. Walsh codes and short PN polynomials are used to spread the forward link signal and distinguish the forward link channels from one another as required by the appropriate terrestrial signal standard and in accordance with the principles of spread spectrum multiple access techniques. Different base stations use time-offset versions of the PN sequence to allow the mobile station to select transmissions from different base stations. The forward link consists of 64-128 logical channels or code channels, as is known in the art. The pilot channel is typically a zero code channel such as found in land-based systems. However, additional pilot channels may be used as desired, for example: in satellite systems that use more code channels.

As is known in the art, and repeated here for clarity, the forward link PN codes comprise walsh codes to provide 64 different channels for terrestrial systems and up to 128 channels for satellite systems, and a short code chip sequence, 2¹⁵One chip long. The short code repeats itself once every 26.6 milliseconds and is used for spreading of the forward link. The short code is called a PN roll (roll) or roll over point at the time it loops back and begins to repeat itself. In the reverse link channel, short codes as well as long codes are used for spreading. The length of the long code is about (2)⁴²-1) chip length while repeating itself every 41.4 days.

In the present invention, the receive path 508 receives a PN sequence at an input port 508 a. The PN sequence includes the correct phase of the associated pilot signal. The phase information is forwarded on the receive path output port 508b to a forward link time tracking device 509 and to a demodulation/decoding unit 510. The forward link time tracking device 509 operates in concert with a reverse link time tracking device 511. When configured in this manner, the forward link timing and the reverse link timing can be integrated and bundled directly together.

The forward link device 509 determines the timing of the arrival of an incoming data stream at the frame boundary, which includes the PN sequence. That is, the device 509 may determine, for example, that the critical point of the number (N) of the arriving frame passes through the antenna connector of the receive path 508, or another specific location in the transmit path, at the same time, the frame boundary of the frame number (N) of the reverse link passes through the same antenna connector, or a specific location, which is measured by the reverse link time tracking device 511. Thus, the forward link time tracking device 509 and the reverse time tracking device 511 establish synchronous timing at the PN sequence level (timing level one) between the forward and reverse link times.

As explained above, the receive path 508 may be followed by a synchronization channel message when the pilot signal has been successfully acquired. The synchronization channel message is not forwarded to the forward link time tracking device 509. Instead, the synchronization channel message is forwarded directly to demodulator/decoder 510, where it can be demodulated and the message informational content decoded. The synchronization channel message includes, among other things, CDMA system level timing information (timing level 2). The system timing information is transmitted to a microprocessor interface 512 and forwarded to the microprocessor 512 via input port 502 c.

The microprocessor 502 finally derives additional timing information in the form of a synchronization word from the timing level 2 information. This derived timing information will be used in downstream or subsequent processing steps, which will be discussed in detail below. For example: in this embodiment, processor 502 provides additional timing information to reverse link time tracking device 511, providing system level timing data, as per path 513. The PN generator 515 provides a reverse link PN sequence to the reverse link time tracking device 511. Based on this, the reverse link PN code timing can be accurately coupled to the forward link PN sequence under the tracking of the device 509.

PN level timing information as well as CDMA system level timing information may be shared between the first ASIC402 and the second ASIC 404. The only prerequisite for the two ASICs to share system-level timing information is that both the first and second ASICs402 and 404 must use compatible PN sequence formats. To satisfy this prerequisite, the PN generator 515 can be programmed to provide a PN sequence that is consistent with the PN format sequence of the second ASIC 404.

To provide a consistent PN sequence format, a control signal is provided from the microprocessor 502 along a connection path 516 to provide instructions for the PN generator for the appropriate PN sequence format required by the second ASIC 404. In accordance with this information, the PN sequence generator 515 then generates a PN sequence that is consistent with the format requirements of the second ASIC 404. As described above with reference to the example embodiment of fig. 4, 5, the second ASIC404 is configured to operate in accordance with the satellite system through user action of the satellite mode switch 304. Thus, the format of the PN sequence for the second ASIC404 is determined according to the satellite signaling standard.

The satellite compatible PN sequence is generated by the sequence generator 515 and mixed with timing information in the reverse link of the reverse link time tracking device 511 to provide a synchronized PN sequence compatible with the second ASIC 404. The synchronized PN sequence is then provided to a transmit path 514. The transmit path 514 includes components such as a transmitter, interleaver, and other baseband and/or IF components. The transmit path 514 provides the synchronized PN sequence to the second switch 408 along the reverse link 406 using the output port 514 a. Second switch 408 is also coupled to and receives instructions, control signals, or commands from microprocessor 502. The processor 502 is configured to provide a control signal instructing the switch 408 to provide the synchronization sequence as an output transmission from an output port 517 a. Alternatively, the control signal may instruct the switch 408 to provide the synchronized PN sequence to the other output port 517 b. When the first ASIC402 and the second ASIC404 share timing information, the switch 408 provides a synchronized PN sequence from its output port 517b to the switch 416.

Switch 416 receives an input from switch 504 through input port 518 a. Alternatively, the switch 416 receives the synchronized PN sequence from the other input port 518 b. The control signal forwarded by the processor 502 indicates to the switch 416 whether to select the signal 507b input at the input 518a or to select the PN sequence via the input 518 b. If the second ASIC404 receives the signal 507b as an input, then the second ASIC404 would be required to independently acquire and derive timing information in the manner discussed above.

On the other hand, for the described embodiment, the third switch 416 receives and forwards through the third switch output port 518c the synchronized PN sequence timing received from the first ASIC402 when activated as a result of the actuation of the mode switch 305. When a 911 emergency call is made from the wireless device or mobile phone 124b, for example, the device user can communicate through the call in traffic on the traffic channel of the first ASIC 402. In a conventional mobile phone, if the user terminal is communicating on the traffic channel, the user's current traffic call will be interrupted and the second ASIC404 will be required to synchronize to the satellite system time and perform GPS measurements. This process may take several seconds to complete and may terminate an ongoing traffic call for the mobile station or wireless device.

However, using the described embodiment to align the time between the first ASIC402 and the second ASIC402 may reduce the time required to perform GPS measurements and increase the accuracy of the measurements. Although the invention is discussed in terms of GPS signals, other air link standards may be used to acquire signals.

As also represented in fig. 5, the second ASIC404 includes a receive path 519 and a correlator 520. The receive path 519 is similar in structure and function to the receive path 508 of the first ASIC402 and includes an input port 519a and an output port 519 b. When the second ASIC404 is required to make timing measurements, the reverse link of the first ASIC402 is injected into the forward link of the second ASIC404 through the input port 519 a. In this regard, for example, instead of receiving a conventional PN sequence input to the input port 519a and then searching for system time, the receive path may now utilize the PN sequence and timing information derived by the first ASIC 402.

The PN sequence is forwarded to correlator 520 through output port 519 b. The correlator 520 searches for or correlates the PN sequence with a local sequence to determine its associated timing offset. In the exemplary embodiment, the correlator 520 receives a control signal from the process 502 along a receive path 521 that instructs the correlator not to demodulate or decode the synchronization channel. When the correlator detects the presence of a PN sequence and determines the timing offset, it forwards the PN sequence and offset to a tracking loop 522 via output port 520 b. The tracking loop 522 monitors the PN sequence to determine PN roll. When PN roll is detected, a detection signal is forwarded to a PN roll generator 523. The PN roll generator 523 generates a PN roll high signal in response to the detected PN roll.

When the processor 502 receives the synchronization word from the microprocessor interface 512, timing information derived based on the synchronization word, as discussed above, is also forwarded by a microprocessor interface 525 to a timing block 524. However, to account for processing and path delays, processor 502 uses a timing technique in which the derived synchronization word is forwarded to timing block 524 in a manner that compensates for the maximum path delay between processor 502 and processor interface 525.

When performing this timing technique, the processor 502 basically notifies the timing block 524 that the system time will be (Y) in (X) number of frame sequences. Timing frame 524 also receives the PN roll high signal from PN roll generator 523. Thus, timing block 524, which receives the PN roll high signal from PN roll generator 523 and the timing technology time tag over interface 525, can accurately determine the correct system time in ASIC 404. The system time may be determined within the accuracy of the desired resolution. The accurate system time is then transmitted along a transmission path 527 or to a GPS acquisition device 528. The GPS acquisition device 528 is configured to receive GPS signals and perform GPS measurements.

To illustrate, the GPS acquisition device 528 can now use this timing information to reduce the amount of search space or the size of the timing window of the timing hypothesis required to acquire the GPS signal. Thus, by using the present invention, the mobile station 124b may reduce the time required to acquire a second timing signal, such as a GPS signal, by reducing the overhead and the number of search attempts required to acquire the signal.

Fig. 6 illustrates another exemplary embodiment using a single reconfigurable multi-mode ASIC 601. In fig. 6, a processing system 600 includes the processor 502 and the tuner 503 shown in fig. 5. For illustrative purposes only, the tuner 503 in fig. 6 IS shown operating between a first mode 602 associated with the IS-95 air link standard and a second mode 603 associated with the W-CDMA air link standard. The control signal provided by the processor 502 instructs the tuner 503 to which RF signal to tune. For example, in the first mode 602, the tuner 503 IS configured to receive RF signals associated with the IS-95 air link standard. The received IS-95 RF signal IS forwarded to receive path 604. Here, the signal format and internal processing is similar to that discussed above with reference to fig. 5. However, in system 600, internal processing is determined based on the particular mode selected in ASIC 602.

The multifunction module 606 includes the forward and reverse link tracking devices, decoders, and PN generators associated with the first ASIC402 shown in fig. 5. Module 606 also includes the correlator tracking loop of fig. 5 and the implementation of the PN roll signal high device associated with the second ASIC 404. A software driven mode control module 610 configures the ASIC602 based on user input selecting an IS-95 compliant operating mode.

In this operational module, all timing and signaling information associated with IS-95 first module 602 IS stored in a memory 612. A transmit path 614 connected to the multifunction module 606 is provided to transmit communication and signaling data along a reverse link 616.

However, in this embodiment, when the user wishes to make a 911 emergency call, the ASIC602 is reconfigured by the mode control module 610 to search for and acquire GPS signals using the GPS acquisition module 618. In this case, all of the timing and synchronization information stored in the memory 610 may be recovered and used in conjunction with the GPS signal search directed by the mode control module 610, as discussed above in connection with the first ASIC 402. Thus, the size of the search window and the time required to acquire the GPS signal may be reduced.

Fig. 7 illustrates an exemplary method 700 for injecting or transmitting reverse link signals from a first ASIC to the forward link of a second ASIC in accordance with the present invention. In a process step 702, timing signals associated with the CDMA pilot channel and CDMA synchronization channel are received in the forward link in the first ASIC 402. In process step 704, correlated PN level sequence data is transmitted over the transmit path 514 relative to the received forward link PN timing correlation. The PN sequence data is transmitted along the reverse link of transmission path 514. The synchronization data is derived from an associated synchronization message on or from the synchronization channel.

The derived synchronization data is received in processor 502 and converted into timing words for forwarding and further processing, as shown in step 706. In step 708, the transmitted data and timing words are received in the second ASIC404, wherein synchronization information is generated from the received transmitted data, as shown in step 710. One or more operations, such as: acquisition of the GPS signal may be performed in accordance with the received timing word data, as shown at step 712.

By using the techniques of these embodiments, multiple ASICs may share system time to enable faster acquisition of timing signals associated with different airlink standards. By using this technique, the time of the technique for obtaining these signals and making GPS measurements can be reduced from seconds to milliseconds. Accordingly, a drop in E911 operation or an inter-system handover can be minimized.

The foregoing description of the preferred embodiments provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention.

Claims (22)

1. An apparatus comprising:

a first communications device comprising at least first and second types of communications paths configured to receive first and second timing signals in the first type of communications path and to transmit data on the second type of communications path, the transmitted data being associated with a received first timing signal;

a processor coupled to the first communication device and configured to receive the second timing signal and generate a timing word from a second timing signal; and

a second communication device includes at least the first type of communication path coupled to the processor and configured to receive the timing word, receive the transmitted data, and derive synchronization information therefrom, the synchronization information being related to the first timing signal, and perform one or more operations in accordance with the received second timing signal and the derived synchronization information.

2. The apparatus of claim 1, wherein the first type of communication path comprises a forward link and the second type of communication path comprises a reverse link.

3. The apparatus of claim 1 wherein said first and second timing signals comprise a pilot signal and a synchronization channel message signal, respectively.

4. The apparatus of claim 1, wherein the first and second communication devices comprise first and second application specific integrated circuits, respectively

5. The apparatus of claim 1, wherein the one or more operations comprise at least deriving timing information related to a second communication device.

6. The apparatus of claim 1, wherein the received timing word comprises an adjustment to compensate for path delay.

7. An apparatus comprising:

a first communications device comprising at least first and second types of communications paths configured to receive first and second timing signals over said first type of communications path and to transmit data over said second type of communications path, said transmitted data being associated with said received first timing signal;

a processor electrically coupled to the first communication device and configured to receive the second timing signal and generate a timing word from the second timing signal; and

a second communication device includes at least a first type of communication path coupled to the processor and configured to receive a timing word therefrom, to receive transmitted data therefrom, and to derive synchronization information, the synchronization information being related to the first timing signal, and to obtain one or more communication signals in accordance with the received second timing signal and the derived synchronization timing information.

8. The apparatus as recited in claim 7 wherein said first type of communication path comprises a forward link and said second type of communication path comprises a reverse link.

9. The apparatus of claim 7 wherein said first and second timing signals comprise a pilot signal and a synchronization channel message signal, respectively.

10. The apparatus of claim 7, wherein the first and second communication devices comprise first and second application specific integrated circuits, respectively.

11. The apparatus of claim 7, wherein the one or more communication signals comprise at least one timing signal associated with a positioning satellite network.

12. The apparatus of claim 7, wherein the received timing word comprises an adjustment to compensate for path delay.

13. An apparatus comprising:

a processor;

a tuner coupled to the processor and configured to receive a plurality of radio frequency signals based on a first processor control signal, the tuner producing a selected frequency signal as an output;

a first switch coupled to the processor having two or more first switch output ports and configured to receive a second processor control signal to receive the selected frequency signal from the tuner and to selectively switch the received selected frequency signal between the two or more first switch output ports.

A first circuit coupled to said microprocessor, said tuner, and said first switch comprising:

a first receive path having an input port coupled to a first of the two or more first switch output ports, the receive path being configured to receive a selected frequency signal through the input port, the received selected frequency signal including a first type timing component and a synchronization command word, the synchronization command word being output to the processor, the processor generating a second type timing component in response thereto;

a time tracking device configured to receive the first and second timing components, to perform a first synchronization timing operation in response to the received first and second timing components, and to generate a synchronization point in accordance with said first synchronization operation;

an encoder generator coupled to the processor and configured to receive a communication message therefrom, generate a data sequence in accordance with the communication message and provide the data sequence to the time tracking device, the time tracking device generating an associated data sequence based on the synchronization point and the communication message, an

A first transmit path configured to receive the sequence of related data and to produce therefrom a synchronized data stream configured to transmit said synchronized data stream using a first propagation path output port;

a second switch electrically coupled to the processor and the first transmit path output port, including two or more second switch output ports, and further configured to receive a third processor control signal to receive the synchronous data stream and to selectively switch the received synchronous data stream between the two or more second switch output ports; a third switch comprising first and second third switch input ports and an output port, wherein the first third switch input port is coupled to a second of the two or more first switch output ports and the second third switch input port is coupled to one of the second switch output ports, the third switch being configured to receive a fourth processor control signal to receive the selected frequency signal using the first third switch input port and the synchronized data stream using the second third switch output port;

a second circuit coupled to the processor and the third switch comprising:

a second receive path having an input port coupled to the third switch output port configured to receive a selected one of the synchronized data streams and a selected frequency signal from the input port; and

a correlator coupled to an output port of a second receive path and configured to detect the presence of a synchronous data stream, the correlator providing the synchronous data stream as an output when the synchronous data stream is received on the second receive path; and

a time measurement mechanism having a first input coupled to the output port of the correlator and another input coupled to said microprocessor, said time measurement mechanism being configured to receive the synchronization data stream from the correlator and the synchronization timing word from said processor and to derive a timing window therefrom.

14. The apparatus of claim 13, wherein the first type of timing component comprises timing information of a pseudo-random noise level.

15. The apparatus of claim 13, wherein the first and second receive paths comprise a forward link.

16. The apparatus of claim 13 wherein the first transmit path comprises a reverse link.

17. A method for acquiring a timing signal in a system comprising a first communication device including at least first and second type communication paths, a second communication device including at least a first type communication path, and a processor, the method comprising the steps of:

receiving first and second timing signals on a first type of communication path on a first communication device;

transmitting data from a second type of communication path of the first communication device, the transmitted data relating to the received first timing signal;

receiving the second timing signal at the processor and converting the second timing signal into a timing word;

receiving at the second communications device (i) the transmitted data and deriving therefrom synchronization information and (ii) a timing word; and

one or more operations are performed in accordance with the received transmission data and the timing word.

18. The method of claim 17, wherein the first and second timing signals comprise a pilot signal and a synchronization channel message, respectively.

19. The method of claim 17, wherein the first type of communication path comprises a forward link and the second type of communication path comprises a reverse link.

20. The method of claim 17, wherein the data comprises a synchronization timing word.

21. An apparatus comprising:

a communication device configured to operate in first and second airlink modes;

at least first and second type communication paths adapted to facilitate communication with a communication device at least during the first airlink mode;

wherein the communication device is configured to (i) receive first and second timing signals over a first type of communication path, the first and second timing signal data representing first and second timing signals, respectively, stored in a memory of the communication device, and (ii) transmit communication data over a second type of communication path, the communication data being transmitted according to the first timing signal data;

wherein the second airlink mode includes at least one first-type communication path configured to facilitate communication with the communication device during operation in the second airlink mode;

wherein the first type communication path of the second airlink mode is configured to receive the transmitted communication data and to generate first type synchronization information therefrom;

a timing mechanism configured to activate and receive the first type of synchronization information during a second airlink mode; and

a processor coupled to the communication device and configured to receive the second timing signal data stored in the memory and generate a second type of synchronization information therefrom, the processor providing the second type of synchronization information to the timing mechanism during activation.

22. The apparatus of claim 21, wherein the first and second airlink modes have compatibility with at least one of satellite, CDMA, W-CDMA, and GSM based wireless communication systems.