The application is a divisional application of Chinese patent application with international application date of 2005, 12 and 7, national phase date of 2007, 6 and 5, application number of 200580041761.0, entitled "method and system for switching antenna and channel allocation in broadband wireless network".
Detailed Description
The combination of OFDMA and spatial processing provides a powerful platform for multi-user broadband communications. A method, apparatus and system are described for easy integration of OFDMA with variously configured antenna arrays. The above-described methods and apparatus allow multi-user diversity to be exploited with simple antenna operation, thus increasing the capacity and performance of the wireless communication system. In one embodiment, channel characteristics indicative of signal reception quality for downlink or bi-directional traffic for each channel (e.g., OFDMA subchannel/antenna resource combination) are measured or estimated at the user. Corresponding channel characteristic information is returned to the base station. The channel characteristic information may also be measured or estimated for uplink or bi-directional signals received at each of the plurality of receive antenna resources. The base station employs channel allocation logic to allocate uplink, downlink, and/or bidirectional channels to a plurality of users based on channel characteristics measured and/or estimated for the uplink, downlink, and/or bidirectional channels.
The benefits of the present invention include simpler hardware (much less expensive than beam forming antenna arrays) and easier processing (much simpler than MIMO) without sacrificing overall system performance. In addition to OFDMA implementations, its general principles can also be applied to FDMA (frequency division multiple access), TDMA (time division multiple access), CDMA (code division multiple access), OFDMA and SDMA (space division multiple access) schemes, as well as combinations of these multiple access schemes.
In the following description, numerous details are set forth in order to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art that the specific details are not required in order to practice the present invention. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.
Some portions of the detailed descriptions which follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the most effective means used by those skilled in the data processing arts to convey the substance of their work to others skilled in the art. An algorithm is here, and generally, considered to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), Random Access Memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, but is not limited to, and each is coupled to a computer system bus.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein.
A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory ("ROM"); random access memory ("RAM"); a magnetic disk storage medium; an optical storage medium; a flash memory device; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); and so on.
SUMMARY
Efficient utilization of spatial diversity in high-speed wireless networks is a challenging task due to the broadband nature of the spatial channel characteristics. In an OFDMA network, the broad spectrum is divided into parallel narrow-band traffic channels (commonly referred to as "subchannels"). The methods described herein provide a method for allocating traffic channels through intelligent traffic channel assignment.
In the communication system described herein, the channel assignment logic performs "channel-aware" traffic channel assignment. In one embodiment, the channel allocation logic provides the required bandwidth and efficient use of spectral resources (e.g., OFDMA traffic channels) and spatial resources (e.g., physical locations of users as they pertain to spatial beamforming), and performs traffic channel allocation based on the wideband spatial channel characteristics of the requesting user and the on-going users (users) for the ongoing service. Also, channels are allocated to users based on the best antenna resources for those users. Thus, the above-described channel allocation provides improved performance over more users than is typically available using conventional channel allocation methods.
In response to a link request from a new user, or when the base station has data to send to a standby user, the logic first estimates the channel characteristics of transmissions received over the OFDMA traffic channels for all or a selected portion of each antenna resource. As used herein, an antenna resource may include a single antenna, or a sub-array of antennas (in an antenna array of a given base station) that are used together to transmit and/or receive signals from users. For example, multiple antennas may be configured to (efficiently) serve as a single antenna resource with improved transmission characteristics (as compared to a single antenna) by using one or more signal diversity schemes (spatial, frequency, and/or time). In one embodiment, the channel characteristics are used along with the channel assignments for the users in traffic to determine which antenna resources are optimal for each user. The channel characteristic data may be stored in registers or other types of storage locations (e.g., databases, files, or similar data structures). In one embodiment, the traffic channel corresponding to the antenna resource with the best communication characteristics is assigned to the access user to satisfy the access user's service request.
Fig. 1 illustrates an exemplary portion of a broadband wireless network 100 including a base station 102, wherein the base station 102 implements the channel selection techniques described herein. Base station 102 includes equipment that supports communication with various users, such as mobile (telephone) users 104 and 106, fixed (location) users 108 and 110, and mobile (PDA) user 112. These include a receive module 114, a transmit module 116, and a channel management component 118, as well as an antenna 120A (also referred to herein as antenna # 1) and an antenna 120B (also referred to herein as antenna # 2).
Typically, a base station communicates with users in the following manner. Data bursts (data bursts) such as cellular packets, IP packets, or ethernet frames are encapsulated into an appropriate data frame format (e.g., IEEE802.16 for WiMAX networks) and forwarded from a network component such as a Radio Access Node (RAN) to an appropriate base station in a given cell. The base station then transmits to the selected user (identified by the data frame) using a unidirectional wireless link called "downlink". Data transmission from the user to the network 100 proceeds in the opposite direction. In this case, the encapsulated data is sent from the user to the appropriate base station using a unidirectional wireless link called the "uplink". The data packets are then forwarded to the appropriate RAN, converted to IP packets, and then transmitted to a destination node in network 100. In some types of broadband wireless networks, bursts of data may be transmitted using a Frequency Division Duplex (FDD) or Time Division Duplex (TDD) scheme. In the TDD scheme, both uplink and downlink share the same RF (radio frequency) channel but do not transmit simultaneously, while in the FDD scheme, uplink and downlink operate on different RF channels but the channels can transmit simultaneously. In general, the unidirectional wireless downlink may include a point-to-point (PP) link, a point-to-multipoint link (PMP), or a MIMO link. The uplink typically includes a PP or PMP link, although MIMO links may also be used.
A plurality of base stations are configured to form a cellular-like wireless network in which, for a given user at any given location, one or more base stations are accessible using a shared medium, the space (air) through which the radio waves propagate. Networks utilizing a shared medium require a mechanism for efficiently sharing the shared medium. The sharing of the air medium is achieved by a suitable channel-based scheme, wherein a respective channel is allocated to each user in the access range of a given base station. Typical channel-based transmission schemes include FDMA, TDMA, CDMA, OFDMA, and SDMA, as well as combinations of these multiple access schemes. Each of these transmission schemes is well known in the art of wireless networking.
To facilitate downlink and uplink communications with various users, the base station 102 provides multiple antennas. For illustrative purposes, these antennas are shown in fig. 1 as antennas 120A and 120B (antennas #1 and # 2). The signals from two or more of the multiple antennas may be combined to support beamforming or spatial multiplexing, or may be used separately for different groups of users using well-known techniques. The plurality of antennas may also be configured in one or more clusters. In general, antennas 120A and 120B represent various antenna types employed in wireless broadband networks, including sector antennas and omni-directional antennas.
In one embodiment, each user is assigned to a respective channel or sub-channel provided by one antenna (or antenna resource when multiple antennas are combined to transmit or receive a signal) at a given base station. For example, in the configuration shown in FIG. 1, mobile subscriber 104 and fixed subscriber 110 are assigned to respective channels supported by antenna 120A, while fixed subscriber 108 and mobile subscribers 106 and 112 are assigned to respective channels supported by antenna 120B. As explained in more detail below, the channel/antenna or sub-channel/antenna for each user is selected based on the best available channel characteristics when a new user enters the network via a given base station (e.g., base station 102). In addition, the channel may be reallocated to the user who is conducting the service based on a change in the measured channel characteristics.
For illustration, the following discussion relates to channel allocation for an OFDMA network. However, this is not meant to be limiting as similar principles may be applied to wireless networks employing other channel-based transmission schemes, including FDMA, TDMA, CDMA, SDMA and OFDMA/SDMA, as well as other combinations of these schemes.
In accordance with an aspect of the present invention, a channel allocation scheme is now disclosed for allocating downlink and/or uplink or shared (bi-directional) channels of respective users to selected antenna resources based on current channel characteristics. The general approach is to assign the channel/antenna or sub-channel/antenna combination with the best channel characteristics to the new user and the user that is doing the service.
Fig. 2 illustrates a set of initial OFDMA channel allocations for the respective users illustrated in fig. 1. In the illustrated embodiment, each of antennas #1 and #2 (120A and 120B) supports N subchannels. Typically, each user is allocated a respective subchannel for a given antenna or antenna resource. In some cases, multiple subchannels may be allocated for the same user. For purposes of illustration, only a single set of subchannel assignments is shown in fig. 2, where the single set illustrates uplink, downlink, or shared (same channel used for both uplink and downlink) channel assignments. It should be appreciated that there will be another set of channel assignments for transmission schemes that employ separate channels for downlink and uplink traffic.
With reference to fig. 1 and 3a, it is now assumed that a new mobile subscriber 122 attempts to initiate a service with base station 102 by initiating a new service request or in conjunction with a handover from another (currently) serving base station (not shown) to base station 102. As described above, it is desirable to allocate the best available channel to the new user. Thus, a mechanism is provided for determining the best available channel.
With further reference to the flow chart of fig. 4a, one embodiment of a process for determining channel characteristics begins at block 400 where a base station broadcasts a beacon signal from each of its antenna resources covering all of the subchannels on the frequency bandwidth allocated to the base station. For example, in an FDMA scheme, a broadcast signal may include a signal that varies in frequency over an allocated bandwidth using a predetermined period. In the CDMA scheme, a test signal transmitted through each CDMA channel varying in a cyclic manner may be used. In a channel scheme that supports multiple channels operating on the same frequency (such as OFDMA), the broadcast signal will include applicable sub-channel/frequency combinations per antenna resource (more details of one embodiment of the OFDMA beacon signal scheme are described below). As a result, the broadcast beacon signal will provide information from which spatial and frequency channel characteristics can be determined. In one embodiment, the beacon signal is broadcast over the management channel in real time. In the case of some time slot based channel schemes (e.g., OFDMA, CDMA, TDMA), it may be necessary to first perform timing synchronization between the base station and the users to enable the users to sufficiently coordinate (e.g., synchronize) with the broadcast beacon signals.
In response to the beacon signal, the user (device) tunes its receiving unit to traverse the various channels (in synchronization with the channel variations in the beacon signal) while measuring the channel characteristics. For example, in one embodiment, signal to interference plus noise ratio (SINR, also commonly referred to as carrier to interference plus noise ratio (CINR) for some types of wireless networks) and/or Relative Signal Strength Indicator (RSSI) measurements are made at the user to obtain channel characteristic measurements or estimates. In one embodiment, the channel characteristic measure is related to the data rate that can be reliably obtained for different channels, as exemplified by the channel characteristic measure data sets corresponding to antennas #1 and #2 shown in fig. 5 (a simplified version is shown in fig. 3 a). For example, it is common to measure such data rates in bits per second per hertz, as shown in fig. 5. In another embodiment, BER measurements are made for each channel/antenna resource combination. In yet another embodiment, quality of service (QoS) parameters such as delay and jitter are measured to obtain channel characteristic data. In yet another embodiment, various indicators of signal quality/performance may be measured and/or estimated to obtain channel characteristic data.
Continuing with block 404 in fig. 4a, after or as channel characteristic measurements are obtained, corresponding data is returned to the base station. In one embodiment, this information is returned via a management channel for such purpose. In response, the best available channel is selected for allocation to the user based on the current channel availability information and the channel characteristic data. Details of the selection process are described below with reference to fig. 6.
Exemplary OFDMA Downlink/Bi-directional Link channel characterization
In one embodiment employed for an OFDMA network, each base station periodically broadcasts pilot OFDM symbols to each user in its cell (or sector). This pilot symbol, often referred to as a sounding sequence or signal, is known to both the base station and the user. In one embodiment, each pilot symbol covers the entire OFDM frequency bandwidth. The pilot symbols may be different for different cells (or sectors). The pilot symbols may be used for a number of purposes: time and frequency synchronization, channel estimation, and SINR measurement for subchannel allocation.
In one embodiment, each of the plurality of antenna resources transmits a pilot symbol simultaneously and each pilot symbol occupies the entire OFDM frequency bandwidth. In one embodiment, each pilot symbol has a length or duration of 128 microseconds with a guard time, the combination of which is approximately 152 microseconds. After each pilot period, there is a predetermined number of data periods followed by another set of pilot symbols. In one embodiment, four data periods follow each pilot to transmit data, and each data period is 152 microseconds in length.
As the pilot OFDM symbols are broadcast, each user continuously monitors the reception of pilot symbols and measures (e.g., estimates) SINR and/or other parameters, including inter-cell interference and intra-cell traffic, for each subchannel. In one embodiment, the user first estimates the channel response, including amplitude and phase, as if there was no interference or noise. Once the channel is estimated, the user calculates interference/noise from the received signal.
During the data traffic period, the user may again determine the interference level. The data traffic period is used to estimate intra-cell traffic and sub-channel interference levels. In particular, the power difference during the pilot and traffic periods may be used to detect the (intra-cell) traffic loading and inter-subchannel interference in order to select the desired subchannel.
In one embodiment, each user measures the SINR of each subchannel (or a set of subchannels corresponding to available subchannels) and reports these SINR measurements to their base station over the access channel. The information feedback from each user to the base station includes SINR values (e.g., peak or average values) for each subchannel. The channel index scheme may be used to identify feedback data for each subchannel; no index is needed if the order of the information in the feedback is known a priori to the base station.
Upon receiving feedback from the user, the base station selects a subchannel to allocate to the user in a manner similar to that described below. After subchannel selection, the base station informs the user of the subchannel assignment through a downlink common control channel, or through a dedicated downlink traffic channel in the case where a connection with the user has been established. In one embodiment, the base station also informs the user of the appropriate modulation/coding rate. Once the basic communication link is established, each user may continue to send feedback to the base station using a dedicated traffic channel (e.g., one or more predefined uplink access channels).
The foregoing scheme determines channel characteristics for the downlink and shared bi-directional link channels. However, it may not be sufficient to predict the uplink channel characteristics. The reason is that multipath fading is generally unidirectional. As a result, a channel that produces good downlink channel characteristics (measured at the receiving user) may not provide good uplink channel characteristics (measured at the receiving base station).
Referring to fig. 3b and 4b, one embodiment of a process for determining channel characteristics for an uplink channel (or optionally a bidirectional shared channel) begins at block 450 (fig. 4 b), where a user performs ranging with each antenna resource at a base station. The term "ranging" is used by the WiMAX (IEEE 802.16) standard to define a set of operations used by a subscriber station (subscriber station) to obtain service availability and signal quality information from one or more base stations. During this process, the subscriber station synchronizes with the base station and a series of messages are exchanged between the subscriber station and the base station. Also, the signal quality measurement value may be obtained by performing CINR and/or RSSI measurements at the base station and/or the subscriber station.
"ranging," as used herein, generally refers to a transmission action initiated by a user to enable uplink channel characteristics to be measured by a base station; thus, ranging includes the aforementioned ranging operations defined by the WiMAX specification for WiMAX networks, as well as other techniques for obtaining uplink channel characteristics. For example, operations similar to those employed during WiMAX ranging may be used for other types of broadband wireless networks. In one embodiment, the user and the base station exchange information about the channel sequence over which the channel characteristic measurements are to be made. For example, in some implementations, the base station may only identify unused uplink channels to measure, thereby reducing the number of measurements to be performed. Optionally, the channel sequence may be known in advance.
Continuing at block 452, based on the channel sequence information, the user traverses the applicable uplink channel while transmitting test data to each base station antenna resource. In general, this may be performed simultaneously for all individual antennas or combined antenna resources, or may be performed separately for each antenna resource. In connection with the transmission of test data over each uplink channel, channel characteristic measurements are made by the base station in block 452 and stored in block 454. In general, the channel characteristic measurements made in block 452 are similar to the channel characteristic measurements performed in block 402 (FIG. 4 a), except that the measurements are now made at the base station rather than at the user. The best available uplink channel to allocate to the user is then selected in block 456 in a manner that will now be described with reference to the operation of fig. 6.
More specifically, fig. 6 shows a process for channel allocation under a common configuration of a base station with a variable number of users (subscribers), antennas (individual antennas or combined antenna resources), and subchannels for each antenna or combined antenna resource. Thus, in fig. 6, a set of data 600 including initial inputs defining the number of users and antennas, the number of subchannels, and the maximum number of subchannels per antenna is provided to the processing operations shown below the data 600.
The operations shown in blocks 604, 606, and 610 are performed for each of users 1 through P, as shown by start and end loop blocks 602 and 612. First, in block 604, the available subchannel with the highest gain is selected among all available antennas (or combined antenna resources, if applicable). As shown in input data block 606, a set of available subchannels for each antenna is maintained and updated in real-time to provide current subchannel assignment information to block 604. Additionally, the channel characteristic profile data measured in blocks 402 and/or 452 (if applicable) is stored in the subscriber channel profile register 608 and updated in real-time. During channel selection for a particular user, corresponding channel characteristic profile data is retrieved from user channel profile register 608 as input to block 604.
Based on the input data from data blocks 606 and 608, in block 610, subchannel k and antenna/are assigned to user i. The process then proceeds to the next user (e.g., user/+ 1) to be assigned a channel comprising a subchannel/antenna combination by operation of block 604 based on the updated input data from data blocks 606 and 608. Typically, these operations are repeated in real time.
These concepts may be more clearly understood from exemplary channel allocation parameters according to the network participants shown in the figures herein. For example, fig. 2 shows an initial situation in which mobile user 106 and fixed user 110 are assigned channels including sub-channels 1 and 6 of antenna #1, respectively, while fixed user 108 is assigned a channel including sub-channel 2 of antenna #2, and mobile users 104 and 112 are assigned channels including sub-channels 5 and M-1 of antenna #2, respectively. For purposes of illustration, these channel assignments represent uplink, downlink, or bi-directional link channel assignments. For the following example, it is assumed that corresponding channel allocation information exists in data block 606.
Now, assume that mobile subscriber 122 (fig. 1, 3a, and 3 b) attempts to enter the network. First, if applicable, channel characteristic measurement data will be collected according to the operations of the flow charts shown in fig. 4a and/or fig. 4 b. This will update the user channel profile register 608. During the processing of block 604, antenna channel characteristic data for each of antennas #1 and #2 will be retrieved from the user channel profile register 608. As described above, exemplary channel characteristic data is shown in fig. 5. Based on this channel characteristic data, a new channel for mobile subscriber 122 is selected in block 610 in conjunction with the available subchannel information shown in fig. 2 and retrieved from data block 606.
According to the exemplary channel characteristic data and sub-channel assignment data in respective fig. 5 and 2, sub-channel 3 of antenna #2 should be assigned to mobile subscriber 122, which represents the available channel with the highest gain (e.g., the available channel with the best channel characteristics). In one embodiment, this may be determined in the following manner. First, a channel having the highest gain is selected for each antenna resource. In this example, this corresponds to channel 1 for antenna #1 and subchannel 3 for antenna # 2. Next, it is determined whether the subchannel is available. For subchannel 1 of antenna #1, this subchannel is already allocated and therefore it is not available. The channel corresponding to the next best gain, which corresponds to subchannel 5, is then selected for antenna # 1. Likewise, a similar determination is made for channel 2. In this example, subchannel 3 is available, which represents the subchannel with the highest gain for antenna # 2. The gain of subchannel 5 for antenna #1 is then compared to the gain of subchannel 3 for antenna # 2. The subchannel/antenna combination resource with the highest gain is then selected for allocation to the new user. This results in selection of subchannel 3 for antenna #2 as the new channel to be assigned to mobile subscriber 122.
At times, processing logic may perform channel reallocation by repeating the process described above with reference to fig. 6. This channel reallocation compensates for any changes in user movement and interference. In one embodiment, each user reports its channel characteristic data. The base station then performs selective reallocation of sub-channels and antenna resources. That is, in one embodiment, some users may be reassigned to new channels, while other channel assignments will remain the same as before. In one embodiment, retraining is initiated by the base station, and in this case, the base station requests one or more particular users to report their updated channel characteristic data. Channel reassignment requests may also be submitted by users when they observe channel degradation.
Fig. 7 is a block diagram of a base station 700 that communicates with multiple users through OFDMA and spatial multiplexing. The base station 700 includes: a receive antenna array 702; a receiver module 703 comprising a set of down-converters 704 coupled to the receive antenna array 700 and an OFDM demodulator 706; a channel characteristics module 708; an active traffic register (one traffic register) 710; OFDMA subchannel channel allocation logic 712; a user channel profile register 608; OFDMA Medium Access Controller (MAC) 714; an OFDM modem 716; a beacon signal generator; an OFDMA transmitter module 718 includes a subchannel formation block 720 and a set of upconverters 722 that provide inputs to respective antenna resources in a transmit antenna array 724.
The uplink signals, including the access signals from the requesting user, are received by receive antenna array 702 and down-converted to baseband by down-converter 704. The baseband signal is demodulated by an OFDM demodulator 706 and further processed by a channel characteristics block 708 to estimate the uplink channel characteristics of the access user using one of the techniques described above or other well-known signal quality estimation algorithms. The estimated or measured channel characteristic data, along with the channel characteristics corresponding to the channels allocated to the incumbent service stored in the subscriber channel profile register 608 and the incumbent service information stored in the incumbent service register 710, is fed to OFDMA subchannel allocation logic 712 to determine channel allocations for the access subscriber and possibly some or all of the subscribers in the ongoing service. The result is sent to OFDMA MAC 714 which controls the overall traffic.
The control signal from OFDMA MAC 714 and downlink data stream 726 are mixed and modulated by OFDM modulator 716 for downlink transmission. Subchannel formation (such as antenna beamforming/switching operations described below with reference to fig. 8) is performed by subchannel formation block 720 using subchannel definition information stored in user channel profile register 608. The output of the subchannel formation block 720 is upconverted by a bank of upconverters 722 and transmitted through a transmit antenna array 724.
The beacon signal generator 717 serves to generate a beacon signal suitable for the underlying transmission scheme. For example, for an OFDMA transmission scheme, the beacon signal generator 717 generates a signal including OFDMA pilot symbols inserted between test data frames.
Details of the functional blocks corresponding to one embodiment of an OFDMA transmitter module 800 for a base station with N antennas are shown in fig. 8. The MAC dynamic channel assignment block 802 is used to select the appropriate antenna resources and subchannels for each of the P users, as is the modem and subchannel assignment block 8041-PIs shown. Based on the modem and subchannel allocation for each user, using signal processing techniques well known in the art of OFDMA transmissionA corresponding OFDMA baseband signal is generated, up-converted and transmitted over an appropriate antenna. The process is performed by a Fast Fourier Transform (FFT) block 804I-NAnd parallel-to-serial (P/S) conversion block 806I-NAnd add periodic prefix (CP) block 804I-NA description is given.
The OFDMA transmitter module 800 performs an antenna switching operation by adjusting the FFT input. For example, for a given user channel, some FFT inputs are set to 1 (meaning used) while other FFT inputs are set to 0 (meaning ignored). OFDMA transmitter module 800 also supports channels supported by transmitting signals simultaneously via multiple antennas.
In general, the operations performed by the processes and functional blocks illustrated in the figures herein and described above are performed by processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a general purpose computer system or a dedicated machine), or a combination of both.
Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features regarded as essential to the invention.