Patent Publication Number: US-7724853-B2

Title: Enabling mobile switched antennas

Description:
CROSS-REFERENCE 
   This application contains subject matter related to U.S. patent application Ser. No. 11/249,770, entitled METHODS AND APPARATUS FOR TRANSMITTING SIGNALS FACILITATING ANTENNA CONTROL, filed on Oct. 13, 2005, the entirety of which is hereby incorporated by reference. 
   BACKGROUND 
   I. Field 
   The following description relates generally to communications systems, and more particularly performing antenna switching to improve frequency diversity in a wireless communication environment. 
   II. Background 
   Wireless networking systems have become a prevalent means to communicate with others worldwide. Wireless communication devices, such as cellular telephones, personal digital assistants, and the like have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. Consumers have become dependent upon these devices, demanding reliable service, expanded areas of coverage, additional services (e.g., web browsing capabilities), and continued reduction in size and cost of such devices. 
   A typical wireless communication network (e.g., employing frequency, time, and code division techniques) includes one or more base stations that provides coverage areas to subscribers as well as mobile (e.g., wireless) devices that can transmit and receive data within the coverage areas. A typical base station can simultaneously transmit multiple data streams to multiple devices for broadcast, multicast, and/or unicast services, wherein a data stream is a stream of data that can be of independent reception interest to a user device. A user device within the coverage area of that base station can be interested in receiving one, more than one or all the data streams carried by the composite stream. Likewise, a user device can transmit data to the base station or another user device. 
   In conventional multiple-input multiple-output (MIMO) receivers, a separate receive chain is required for each receive antenna. A strip channel is a dedicated resource that may be utilized by a base station for broadcasting. For example a non-beacon strip channel may permit a base station to broadcast information in a prescribed format, when information bits may be coded across one or more strip channels. However, conventional strip channels lack robustness when confronted with channel frequency selectivity, unreliable channel estimation, or the like. An unmet need exists in the art for systems and/or methodologies that mitigate interference and improve frequency diversity to overcome the afore-mentioned deficiencies. 
   SUMMARY 
   The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview, and is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later. 
   According to various aspects, a method of decoding a communication signal may comprise receiving a set of symbols containing a plurality of information bits, dividing the received set of symbols into a plurality of subsets of symbols, each subset corresponding to the input of an inner code demodulation selecting a set of initial a priori values of the inner code demodulation for each subset of symbols, and demodulating each subset of symbols, using the initial a priori values of the subset of symbols and an inner code generator matrix, to generate a plurality of first soft information values as the output of the inner code demodulation. The method may further comprise associating each of the first soft information values to one of the plurality of information bits using an outer code generator matrix, calculating a plurality of second soft information values as the output of the outer code demodulation, wherein each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit, determining a new set of a priori values of the inner code demodulation for each subset of symbols, using the second soft information values and the outer code generator matrix, and replacing the initial a priori values with the new a priori values, and repeating the demodulating, associating, calculating and determining actions at least once. 
   According to another aspect, an apparatus that facilitates decoding a communication signal, comprising a receiver that receives a set of symbols containing a plurality of information bits and divides the received set of symbols into a plurality of subsets of symbols, a decoder that selects a set of initial a priori values of the inner code demodulation for each subset of symbols, and an inner code demodulator that demodulates each subset of symbols, using the initial a priori values of the subset of symbols and an inner code generator matrix, to generate a plurality of first soft information values. The apparatus may further comprise an interleaver that associates each of the first soft information values to one of the plurality of information bits using an outer code generator matrix; an outer code demodulator that calculates a plurality of second soft information values, wherein each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit, and a de-interleaver that determines a new set of a priori values of the inner code demodulation for each subset of symbols, using the second soft information values and the outer code generator matrix, and replaces the initial a priori values with the new a priori values for a next iteration of demodulation of the subsets of symbols. 
   Another aspect relates to an apparatus that facilitates decoding a signal that enables antenna switching at a wireless terminal, comprising means for receiving a set of symbols containing a plurality of information bits, means for dividing the received set of symbols into a plurality of subsets of symbols, each subset corresponding to the input of an inner code demodulation, means for selecting a set of initial a priori values of the inner code demodulation for each subset of symbols, and means for demodulating each subset of symbols, using the initial a priori values of the subset of symbols and an inner code generator matrix, to generate a plurality of first soft information values as the output of the inner code demodulation. The apparatus may further comprise means for associating each of the first soft information values to one of the plurality of information bits using an outer code generator matrix, means for calculating a plurality of second soft information values as the output of the outer code demodulation, wherein each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit, means for determining a new set of a priori values of the inner code demodulation for each subset of symbols, using the second soft information values and the outer code generator matrix, and replacing the initial a priori values with the new a priori values, and means for repeating the demodulating, associating, calculating and determining actions at least once. 
   Still another aspect relates to a computer-readable medium that stores computer-executable instructions for receiving a set of symbols containing a plurality of information bits, dividing the received set of symbols into a plurality of subsets of symbols, selecting a set of initial a priori values of the inner code demodulation for each subset of symbols, and demodulating each subset of symbols, using the initial a priori values of the subset of symbols and an inner code generator matrix, to generate a plurality of first soft information values. The instructions may further comprise associating each of the first soft information values with one of the plurality of information bits using an outer code generator matrix, calculating a plurality of second soft information values, wherein each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit, determining a new set of a priori values of the inner code demodulation for each subset of symbols, using the second soft information values and the outer code generator matrix, and replacing the initial a priori values with the new a priori values, and repeating the demodulating, associating, calculating and determining actions at least once. 
   Yet another aspect relates to a processor that executes computer-executable instructions for decoding a signal that enables antenna switching in a wireless terminal, the instructions comprising receiving a set of symbols containing a plurality of information bits, dividing the received set of symbols into a plurality of subsets of symbols, selecting a set of initial a priori values of the inner code demodulation for each subset of symbols, and demodulating each subset of symbols, using the initial a priori values of the subset of symbols and an inner code generator matrix, to generate a plurality of first soft information values. The instructions may further comprise associating each of the first soft information values with one of the plurality of information bits using an outer code generator matrix, calculating a plurality of second soft information values, wherein each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit, determining a new set of a priori values of the inner code demodulation for each subset of symbols, using the second soft information values and the outer code generator matrix, and replacing the initial a priori values with the new a priori values, and repeating the demodulating, associating, calculating and determining actions at least once. 
   According to other aspects, a method of encoding a strip symbol for transmission to a wireless terminal in a wireless communication environment may comprise encoding an information bit vector with an outer code to generate a bit matrix using an outer code generator matrix generating a codeword for each row in the bit matrix using an inner code generator matrix, and concatenating the generated codewords into a single codeword. The method may further comprise mapping the concatenated codeword to a number of modulation symbols, and mapping the modulation symbols to a subset of tones in the strip symbol. 
   According to another aspect, an apparatus that facilitates encoding a strip symbol for transmission to a wireless terminal in a wireless communication environment may comprise an encoder that encodes an information bit vector with an outer code to generate a bit matrix using an outer code generator matrix, generates a codeword for each row in the bit matrix using an inner code generator matrix, concatenates the generated codewords into a single codeword. The apparatus may further comprise a processor that maps the concatenated codeword to a number of modulation symbols and maps the modulation symbols to a subset of tones in the strip symbol, and a transmitter that transmits the strip symbol. 
   Yet another aspect relates to an apparatus that facilitates encoding a strip symbol for transmission to a wireless terminal, comprising means for encoding an information bit vector with an outer code to generate a bit matrix using an outer code generator matrix, means for generating a codeword for each row in the bit matrix using an inner code generator matrix, as well as means for concatenating the generated codewords into a single codeword. The apparatus may additionally comprise means for mapping the concatenated codeword to a number of modulation symbols, and means for mapping the modulation symbols to a subset of tones in the strip symbol. 
   A further aspect relates to a computer-readable medium that stores computer-executable instructions for encoding an information bit vector with an outer code to generate a bit matrix using an outer code generator matrix, and generating a codeword for each row in the bit matrix using an inner code generator matrix. The instructions may further comprise concatenating the generated codewords into a single codeword, mapping the concatenated codeword to a number of modulation symbols, and mapping the modulation symbols to a subset of tones in the strip symbol. 
   According to still a further aspect, a processor that executes computer-executable instructions for encoding a strip symbol for transmission to a wireless device may execute instructions comprising encoding an information bit vector with an outer code to generate a bit matrix using an outer code generator matrix, generating a codeword for each row in the bit matrix using an inner code generator matrix, and concatenating the generated codewords into a single codeword. The processor may further execute instructions for mapping the concatenated codeword to a number of modulation symbols, and mapping the modulation symbols to a subset of tones in the strip symbol. 
   According to still other aspects, a method of permitting antenna switching in a wireless terminal in a wireless communication environment may comprise performing a coherent demodulation protocol during a second transmission time period of a first superslot and estimating an SNR for a first antenna, switching to at least a second antenna at the end of the first superslot, and receiving a bit-interleaved signal having information bits spread across a frequency spectrum for one or more strip symbols. The method may further comprise estimating an SNR for at least a second antenna during a first transmission time period of a subsequent super slot, performing a non-coherent detection protocol during SNR estimation for the at least second antenna, comparing the SNRs for each of the antennas, and selecting an antenna for the subsequent superslot as a function of the estimated SNRs. 
   According to another aspect, an apparatus that facilitates antenna switching in a wireless terminal may comprise a coherent demodulator that demodulates a signal received during a second transmission period of a first superslot, a receiver that receives a bit-interleaved signal having information bits spread across a frequency spectrum for one or more strip symbols, and a processor that estimates an SNR for a first antenna during the first superslot, switches to at least a second antenna at the end of the first superslot, and estimates an SNR for at least the second antenna during a first transmission period of a second superslot. The apparatus may further comprise a non-coherent demodulator that demodulates the strip channel during SNR estimation for the at least second antenna, wherein the processor compares the SNRs for each of the antennas and selects an antenna for the second superslot as a function of the estimated SNRs. 
   Another aspect relates to an apparatus that facilitates antenna switching in a wireless terminal in a wireless communication environment, comprising means for performing a coherent demodulation protocol during a second transmission time period of a first superslot and estimating an SNR for a first antenna, means for switching to at least a second antenna at the end of the first superslot, and means for receiving a bit-interleaved signal having information bits spread across a frequency spectrum for one or more strip symbols. The apparatus may additionally comprise means for estimating an SNR for at least a second antenna during a first transmission time period of a subsequent superslot, means for performing a non-coherent detection protocol during SNR estimation for the at least second antenna, means for comparing the SNRs for each of the antennas, and means for selecting an antenna for the second superslot as a function of the estimated SNRs. 
   Yet another aspect relates to a computer-readable medium having stored thereon computer-readable instructions for performing a coherent demodulation protocol during a first superslot and estimating an SNR for a first antenna, switching to a second antenna at the end of the first superslot, and receiving a bit-interleaved signal having information bits spread across a frequency spectrum for one or more strip symbols. The instructions may further comprise estimating an SNR for at least a second antenna during a first transmission time period of a subsequent superslot, performing a non-coherent detection protocol during SNR estimation for the at least second antenna, comparing the SNRs for each of the antennas, and selecting an antenna for a second transmission period of the subsequent superslot as a function of the estimated SNRs. 
   According to a further aspect, a processor that executes instructions for switching between multiple receive antennas in a wireless terminal may execute instructions comprising performing a coherent demodulation protocol during a second transmission time period of a first superslot and estimating an SNR for a first antenna, switching to at least a second antenna at the beginning of a first transmission time period of a subsequent superslot, receiving a bit-interleaved signal having information bits spread across a frequency spectrum for one or more strip symbols, and estimating an SNR for at least a second antenna during the first transmission time period of the subsequent superslot. The processor may further execute instructions for performing a non-coherent detection protocol during SNR estimation for the at least second antenna, comparing the SNRs for each of the antennas, and selecting an antenna for a second transmission period of the subsequent superslot as a function of the estimated SNRs. 
   To the accomplishment of the foregoing and related ends, certain illustrative aspects are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the claimed subject matter may be employed and the claimed subject matter is intended to include all such aspects and their equivalents. Other advantages and novel features may become apparent from the following detailed description when considered in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a transmission channel overview with respect to time that facilitates to facilitate understanding of strip symbol structure and wireless terminal antenna analysis, in accordance with one or more aspects described herein. 
       FIG. 2  illustrates a system comprising components in an exemplary wireless terminal comprising a receiver RF chain, in accordance with various aspects presented herein. 
       FIG. 3  illustrates a system with various components in a wireless terminal comprising a receiver RF chain, in accordance with various aspects presented herein. 
       FIG. 4  is an illustration of a system that facilitates performing multiple iterations of a soft demodulation and interleaving protocol to refine a received signal and permit antenna switching in a wireless device with multiple antennas and a single receiver chain, in accordance with one or more aspects. 
       FIG. 5  is an illustration of a methodology for performing antenna switching in a wireless device with multiple receive antennas and a single receiver chain, in accordance with one or more aspects. 
       FIG. 6  illustrates a methodology for decoding a communication signal using an iterative SISO non-coherent demodulation protocol to demodulate and interleave concatenated code, in accordance with one or more aspects. 
       FIG. 7  is an illustration of a methodology for encoding a communication signal comprising a strip symbol for transmission to a wireless terminal, in accordance with one or more aspects. 
       FIG. 8  illustrates a system that facilitates antenna switching in a wireless terminal with multiple receive antennas per receive chain, in a communication environment, in accordance with one or more aspects described herein. 
       FIG. 9  illustrates a system that facilitates decoding concatenated-code signals received at a wireless terminal by performing an iterative soft-demodulation and interleaving algorithm, in accordance with various aspects. 
       FIG. 10  is an illustration of a system that facilitates encoding a strip symbol in a transmission signal for a wireless terminal, in accordance with various aspects. 
       FIG. 11  illustrates a network diagram of an exemplary communications system implemented in accordance with the present invention. 
       FIG. 12  illustrates an exemplary base station implemented in accordance with the present invention. 
       FIG. 13  illustrates an exemplary wireless terminal implemented in accordance with the present invention. 
       FIG. 14  is an illustration of a wireless communication environment that can be employed in conjunction with the various systems and methods described herein. 
   

   DETAILED DESCRIPTION 
   The claimed subject matter is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the claimed subject matter. It may be evident, however, that such subject matter may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the claimed subject matter. 
   Furthermore, various aspects are described herein in connection with a user device. A user device can also be called a system, a subscriber unit, subscriber station, mobile station, mobile device, remote station, remote terminal, access terminal, user terminal, terminal, user agent, or user equipment. A user device can be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a PDA, a handheld device having wireless connection capability, or other processing device connected to a wireless modem. 
   Moreover, aspects of the claimed subject matter may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof to control a computer or computing components to implement various aspects of the claimed subject matter. The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips . . . ), optical disks (e.g., compact disk (CD), digital versatile disk (DVD) . . . ), smart cards, and flash memory devices (e.g., card, stick, key drive . . . ). Of course, those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope or spirit of what is described herein. 
   Various aspects described herein relate to coding and modulation to improve frequency diversity in a wireless communication environment, such as an orthogonal frequency division multiplexing communication environment. For instance, information bits may be spread across a bandwidth spectrum through a bit-interleaving protocol, and coding and modulation may be performed to facilitate performing a non-coherent demodulation protocol at a receiver, thereby mitigating a need for channel state information. Soft demodulation techniques may be utilized in conjunction with concatenated code t permit a wireless terminal to switch between antennas when a strip channel is received through multiple antennas. 
     FIG. 1  illustrates a transmission channel overview  100  with respect to time that facilitates the understanding of strip symbol structure and wireless terminal antenna analysis, in accordance with one or more aspects described herein. The transmission channel  100  comprises a strip symbol  102 , which may comprise, for example, 113 tones, 56 of which may be utilized to transmit data, training information etc., and have a non-zero energy associated with them, while the remaining tones are zero energy tones, known as null tones, that do not carry any signal transmission energy. In some embodiments, the tones may be divided into a plurality of (e.g., eight) tone subsets, for example tone set  104 . Each tone set includes 7 non-zero energy tones and possibly null tones. In each tone subset, the 7 non-zero energy tones may be interspersed with null tones. As illustrated, strip symbol  102  comprises 113 tones, and a tone subset  104  includes non-zero energy tones, numbered  1 - 7  and interspersed with null tones (labeled as “X”). In some embodiments, each tone subset  104  may comprise a training tone  106  on which a known symbol is transmitted to facilitate channel estimation. Training tone  106  may be a tone with a different non-zero energy level than the other non-zero energy tones in tone subset  104 , and may be consistent between tone sets and/or strip symbols (e.g., always tone  3 , always to 5, etc.) or may vary between tone sets and/or strip symbols. According to an example, tone  4  may be a training tone in all tone subsets in all strip channels. According to another example, tone  3  may be a training tone in all tone sets in a first strip symbol, tone  4  may be a training tone in all tone subsets in a second strip symbol, yet another tone (e.g., any tone  1 - 7 ) may be a training tone in a third strip symbol, and so on. According to yet another example, training tones in different subsets may be randomly assigned and/or selected. Furthermore, any permutation of training tones, tone sets, and strip symbols may be implemented, so long as each tone set has a training symbol. According to some aspects, the training tone  106  is the middle tone among the 7 non-zero energy tones in the tone subset  104 . Strip symbol  108  follows strip symbol  102 . In some embodiments, the set of non-zero energy tones in strip symbol  102  is different from the set of non-zero energy tones in strip symbol  108 . 
   Strip symbols  102  and  108  may be transmitted at the beginning portion of a superslot (e.g., approximately 11.4 milliseconds long). Consider a wireless terminal equipped with multiple antennas. In  FIG. 1 , a superslot includes a first time period in which the strip symbols are sent and a second time period in which the non-strip symbols are sent. For example, the first superslot of  FIG. 1  includes strip symbols  102  and  108  as the first time period and the non-strip symbols in the remaining time period as the second time period. 
   Suppose that the second time period of the first superslot is received by a wireless terminal over a first channel, H 1 , via a first antenna, Antenna  1 . In one or more embodiments, a pilot signal is sent in the second time period of first superslot. The wireless terminal can thus estimate the channel H 1  and use a coherent demodulation protocol, denoted as F 1 , to decode the received signal. The wireless terminal may further evaluate the value of SNR for Antenna  1 . 
   Then, in the first time period of the second superslot, the wireless terminal may switch to use different antennas, e.g., antenna  2  in the first strip symbol of the second superslot and antenna  3  in the second strip symbol of the second superslot, to receive the signal. As a result, the channel is changed to H 2  and H 3  in the first and second strip symbols respectively, as shown in  FIG. 1 . Note that channel H 2  or H 3  may be different from channel H 1  due to the change of the receive antenna. Therefore, the channel estimation of H 1  obtained in the first superslot may not be applicable for channel H 2  or H 3 . Hence, the wireless terminal uses a non-coherent demodulation protocol, F 2 , to decode the received signal in the strip symbols. The term “non-coherent” means that the modulation of the signal received in the strip symbols does not depend on the signal received in a preceding time period, e.g., in the second time period of the first superslot. The wireless terminal may further evaluate an SNR for one or more other antennas and/or channels (e.g., H 2 , H 3 , etc.) received thereby. SNRs may be measured, for instance, during the zero-energy tones (e.g., interference may be quantified) and null tones in each strip symbol. The SNRs for the one or more other antennas may be compared to the SNR for the first antenna, determined during the previous superslot, and the wireless terminal may switch to the antenna (Antenna X shown in  FIG. 1 ) as a function of the comparison of the measured SNRs. For example, the wireless terminal may select the antenna of the highest measured SNR to be used in the second time period of the second superslot. The above procedure may repeat in the subsequent superslots to provide an iterative method by which antenna reception capability is continuously monitored and evaluated to enable a wireless terminal with multiple antennas to switch between them while utilizing a single receiver chain. 
   In accordance with some aspects, a three-antenna wireless terminal can receive a signal with two strip symbols  102  and  108  at the beginning of each superslot to permit non-coherent demodulation of two unused antennas at each superslot. According to this example, the wireless terminal uses one antenna to receive non-strip symbols in a superslot, uses coherent modulation to decode non-strip symbols, and measures the SNR. The wireless terminal may switch to the other two unused antennas during the strip symbols of the subsequent superslot and perform the non-coherent demodulation protocol on each strip symbol to decode the signal. The wireless terminal further determines the SNR for the respective antennas using the strip symbols. The wireless terminal then selects one antenna to use in the non-strip symbols in the subsequent superslot based on the measured SNRs of the three antennas. It will be appreciated that while  FIG. 1  and the foregoing example relate to a 3-receive-antenna wireless terminal, more or fewer receive antennas may be utilized and a corresponding number of strip symbols may be encoded and transmitted by a base station and received by the wireless terminal to facilitate antenna switching. 
   Encoding and/or modulation of the strip symbols may occur in various manners in conjunction with one or more aspects. Decoding of the strip symbols need not rely on the use of preceding symbols. In some embodiments, the strip symbols may be encoded with a vector, low-density parity check (LDPC) encoding scheme. In particular, the input is a number of information bits, e.g., 60 bits, and the output is a number of coded bits, e.g., 288 bits. The 60-bit vector may be expanded into a 64-bit vector by adding four zeros at the end of the information vector, which may be denoted as u=[u 59 , u 58 , . . . , u 0 ], where u 59  is the most significant bit (MSB) and u 0  is the least significant bit (LSB). The expanded information vector may then be denoted as u=[u 59 , u 58 , . . . , u 0 , 0, 0, 0, 0]. A 304-bit codeword vector x=[x 303 , x 302 , . . . , x 0 ] may be formed from a vector LDPC codes with certain parity check matrix, where x 303  is the MSB and x 0  is the LSB. A 288-bit output vector may be obtained by shortening the codeword vector x. For instance, the 12 most significant bits in the codeword may be punctured so that the next 288 bits in the codeword become the output vector, and the remaining 4 LSBs are similarly punctured. The output vector is given as y=[x 291 , x 290 , . . . , x 4 ], and may be mapped to  288  modulation symbols using the BPSK modulation scheme. 
   The 288 modulation symbols are sent in 6 strip symbols, each for 48 modulation symbols. That is, of the 56 available non-zero energy tone-symbols in each strip symbol, 8 are training tone symbols (one per tone set), resulting in 48 tone-symbols to which modulation symbols may be mapped. In the aspect shown in  FIG. 1 , a strip symbol comprises 56 non-zero energy tones, which are divided into 8 tone subsets and each subset comprises 7 non-zero energy tones. In the set of 48 modulation symbols for a given strip symbol, the first 6 modulation symbols are sent in the first tone subset as follows: the first 3 modulation symbols are sent in the first 3 tones of the tone subset, the other 3 modulation symbols are sent in the last 3 tones of the tone subset, and a known modulation symbol is sent in the middle tone of the tone subset, which can be used by the wireless terminal as a training symbol to learn the channel. The known symbol may be transmitted as the same power as the remaining 6 modulation symbols, or at a higher power. Similarly, the next 6 modulation symbols are sent in the second tone subset, and so on. 
   In another aspect, the strip symbols may be encoded with a concatenated code. Specifically, one strip symbol is to encode an information bit vector u=[u 0 , u 1 , u 2 , u 3 , u 4 ]. First, an outer code is used to form a 21-bit vector. For example, the outer code can be described using a 7×3 matrix, such as: 
                   TABLE 1                              u   21     =     [         u0       u2       u4           u1       u3       u4           u0       u1       u4           u1       u2       u3           u0       u2       u3           u1       u3       u4           u0       u2       u4         ]                                    
Each row comprises 3 bits. For each row in the matrix, an 8-bit codeword may be generated using an inner code generator matrix, G 3,8 , such as: 11110000, 11001100, 10101010. For instance, the first row of the 7×3 matrix is [u 0 , u 2 , u 4 ], and, therefore, the 8-bit codeword is equal to [u 0 , u 2 , u 4 ] G 3,8 . A total of seven 8-bit codewords may be concatenated to form a 56-bit codeword, where the 8 MSBs are generated from the first row of the 7×3 matrix, the next 8 MSBs are generated from the second row, and so on. The 56-bit concatenated codeword may then be mapped to 56 modulation symbols, e.g., using the BPSK modulation scheme. The 56 modulation symbols are sent in the non-zero energy tones of a strip symbol respectively. Note that in order to achieve frequency diversity, the outer code ensures that any information bit (u 0 , u 1 , u 2 , u 3 , u 4 ) appears in multiple rows, which will then be encoded by multiple inner codewords. For example, u 0  appears in the first, third, fifth, and seventh rows. Those codewords will be mapped to tones spanning a wide frequency range in the strip symbol.
 
   In another example, an information vector may be denoted as u=[u 0 , u 1  . . . , u 13 ]. First, an outer code is used to form a 21-bit vector. For example, the outer code can be described using a 7×3 matrix, such as: 
                   TABLE 2                              u   42     =     [         u5       u1       u12           u5       u2       u0           u2       u3       u1           u3       u10       u4           u8       u5       u6           u0       u10       u7           u3       u7       u11           u7       u4       u8           u8       u9       u2           u9       u4       u12           u10       u11       u6           u11       u9       u13           u12       u13       u6           u13       u0       u1         ]                                    
Each row comprises 3 bits. For each row in the matrix, an 8-bit codeword may be generated using an inner code generator matrix, G 3,8 , such as: 11110000, 11001100, 10101010. For instance, the first row of the 14×3 matrix is [u 5 , u 1 , u 12 ], and, therefore, the 8-bit codeword is equal to [u 5 , u 1 , u 12 ] G 3,8 . A total of fourteen 8-bit codewords may be concatenated to form a 112-bit codeword, where the 8 MSBs are generated from the first row of the 14×3 matrix, the next 8 MSBs are generated from the second row, and so on. The 112-bit concatenated codeword may then be mapped to 112 modulation symbols, e.g., using the BPSK modulation scheme. The 112 modulation symbols are sent in the non-zero energy tones of two strip symbols respectively.
 
     FIG. 2  illustrates a system  200  comprising components in an exemplary wireless terminal comprising a receiver RF chain, in accordance with various aspects presented herein. System  200  utilizes a switcher  208  to select one out of the plurality of N antenna elements ( 202 ,  204 ,  206 ). Received signals are routed through the selected antenna to the RF receiver chain, while received signals on the other, non-selected, antennas are not forwarded. Switcher  208  is shown coupled to a first antenna  202 . The switcher may be controlled to switch between antennas based on various information, including time period boundaries. This aspect may be viewed from a functional equivalency standpoint in that the switcher  208  may comprise a set of controllable gain elements (not shown) in which one value is set equal to one, corresponding to the selected antenna, and the other values are set equal to zero, corresponding to the other antennas. 
     FIG. 3  illustrates a system  300  with various components in a wireless terminal comprising a receiver RF chain, in accordance with various aspects presented herein. According to some aspects, multiple “compound” antenna patterns are possible. For instance, system  300  includes a plurality of antenna elements ( 302 ,  304 ,  306 ) coupled to a first set of gain elements ( 308 ,  310 ,  312 ), with gain values (G 1 , 1 , G 2 , 1 , GN, 1 ), respectively. The output of the first set of gain elements ( 308 ,  310 ,  312 ) is input to a first combining circuit  314 . Antenna elements ( 302 ,  304 ,  306 ) are also coupled to a second set of gain elements ( 308 ′,  310 ′,  312 ′), with gain values (G 1 , 2 , G 2 , 2 , GN, 2 ), respectively. The output of the second set of gain elements ( 308 ′,  310 ′,  312 ′) is input to a second combining circuit  314 ′. Additional sets of gain elements each with a corresponding combining circuit may be implemented. System  300  also includes a switcher  316  which couples one of the outputs of one of the combining circuits ( 314 ,  314 ′) to itself and is coupled to the receiver&#39;s RF chain input. 
   Each antenna pattern is in effect created by the weighted sum of the N antenna elements. Different antenna patterns differ in their weighing coefficients, gain values of the a set of gain elements, e.g., (G 1 , 1 , G 2 , 1 , . . . , GN, 1 ), (GN, 1 , G 1 , 2 , . . . , GN, 2 ). The weighting coefficients, sometimes referred to a gain values, can be complex or real values. The gain values may be fixed, predetermined or programmable, adjustable, etc. 
     FIG. 4  is an illustration of a system  400  that facilitates performing multiple iterations of a soft demodulation and interleaving protocol to decode a received signal in a non-coherent manner, in accordance with one or more aspects. The signal is encoded with a concatenated code as illustrated in the embodiments of Table 1 and Table 2. 
   For the concatenated code, it is possible to formulate the overall generator matrix and to derive the optimal, e.g., maximal likelihood, decoding algorithm. However, the optimal decoding algorithm may be computationally complex. The iterative decoder  402  takes advantage of the concatenated coding structure and can approach the performance of the optimal decoder with a few iterations. Advantageously, the complexity is significantly reduced. 
   The decoder  402  may receive a concatenated code input signal, for example a strip symbol received in a superslot as described with regard to Table 1 or 2 in  FIG. 1 , and may initiate a soft-input soft-output demodulation protocol that utilizes an inner code demodulator  404 , an interleaver  406 , an outer code demodulator  408 , and a de-interleaver  410 . For example, a set of symbols containing a plurality of information bits may be received by inner code demodulator  404 , which may then divide the received symbol set into a plurality of symbol subsets. Decoder  402  may select a plurality of a priori values for inner code demodulation of the symbol subsets, and inner code demodulator  404  may demodulate the symbol subsets using the a priori values and an inner code generator matrix to generate a plurality of soft information output values. The soft information output values may be interleaved by interleaver  406  and associated with one of the plurality of information bits by outer code modulator  408  (e.g., using an outer code generator matrix). De-interleaver  410  may calculate a plurality of second soft information values as an output of the outer code demodulator  408 , where each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit. The second soft information values may then be utilized to determine a new set of a priori values for use in a next iteration of the inner code demodulation of the received input symbols, and so on, as indicated by the circular arrow in  FIG. 4 . 
   Consider Table 1 as an example. First, the received signal may be demodulated for the inner code, whose generator matrix may be given as G 3,8 , to generate the soft decoding values of each row in Table 1, in particular, the soft values X 01 , X 21 , X 41  of [u 0 , u 2 , u 4 ] of the first row, the soft values X 12 , X 32 , X 42  of [u 1 , u 3 , u 4 ] of the second row, and so on. Those soft values are called the output soft values of the inner code (e.g., the inner code demodulator  404 ). 
   The outer code demodulator  408  provides an additional coding protection for any given information bit. For example, note that for bit u 0  the first, third, fifth, and seventh rows all provide the soft values. Ideally those soft values are identical. However, because of interference and noise in the received signal, they may not be identical in the first round of iteration. The interleaver  406 , outer code demodulator  408 , and de-interleaver  410  take the output soft values of the inner code and calculate the output soft values of the outer code. For example, denote the output soft values of the inner code in the first, third, fifth, and seventh rows for bit u 0  to be X 01 , X 03 , X 05  and X 07  respectively. Then for bit u 0 , the output soft value of the outer code for the first row, denoted as Y 01  may be calculated from X 01 , X 03 , X 05  and X 07 , e.g., Y 01 =average (X 03 , X 05 , X 07 ). Similarly, for bit u 0 , the output soft value of the outer code for the third row, denoted as Y 03  may be calculated from X 01 , X 03 , X 05  and X 07 , e.g., Y 03 =average (X 01 , X 05 , X 07 ). In another example, one can set Y 01  and Y 03  to be the same, e.g., equal to average (X 01 , X 03 , X 05 , X 07 ). 
   The output soft values of the outer code demodulator are then de-interleaved and provided back to the inner code demodulator  404  to improve the inner code demodulation. In particular, now the inner code demodulator  404  can take the original received signal and the de-interleaved output soft values of the outer code into account to generate the improved soft decoding values of each row. For example, in the first row, the inner code demodulator  404  uses the original received signal and Y 01 , Y 21 , Y 41 , and generates a new set of X 01 , X 21 , and X 41 . Here, Y 01 , Y 21 , Y 41  are the output soft values of the outer code for bits u 0 , u 2 , u 4  of the first row respectively, and X 01 , X 21 , and X 41  are the output soft values of the inner code for bits u 0 , u 2 , u 4  of the first row respectively. The above procedure repeats for all the other rows to generate a new set of the output soft values of the inner code. With the new output soft values of the inner code, the interleaver  406 , outer code demodulator  408 , and de-interleaver  410  can generate a new set of output soft values of the outer code. The above iterative procedure repeats until certain termination criterion is met. 
   Referring to  FIGS. 5-7 , methodologies relating to performing an iterative SISO non-coherent demodulation protocol upon a received concatenated code signal to facilitate antenna switching in a wireless terminal are illustrated. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be utilized to implement a methodology in accordance with the claimed subject matter. 
     FIG. 5  is an illustration of a methodology  500  for performing antenna switching in a wireless device with multiple receive antennas and a single receiver chain, in accordance with one or more aspects. For example, method  500  may facilitate performing various actions set forth above with regard to  FIG. 1  in order to achieve antenna switching as described therein. At  502 , a coherent demodulation protocol may be performed during a second transmission period of a first superslot and an SNR for a first antenna may be estimated. For instance, a superslot may include a first time period in which strip symbols are sent and a second time period in which the non-strip symbols are sent. For example, the first superslot described above with regard to  FIG. 1  includes strip symbols as the first time period and the non-strip symbols in the remaining time period as the second time period. According to an aspect, a pilot signal may be sent in the second time period of first superslot. The wireless terminal may thus estimate the channel H 1  corresponding to the first antenna and use a coherent demodulation protocol, to decode the received signal. For example, the wireless device may receive a set of pilots and derive channel estimation, which enables the wireless device to perform coherent demodulation for the signal received in the second time period of the first superslot. 
   At  504 , a determination whether the first superslot is complete and/or whether a first transmission time period of the second superslot is imminent, may be made. If the first superslot is complete, a switch from the first antenna to a second antenna may be made, at  506 , to assess an SNR there for. In the first time period of the second superslot, the wireless terminal may switch to different antennas, e.g., antenna  2  in the first strip symbol of the second superslot and antenna  3  in the second strip symbol of the second superslot, to receive the signal. As a result, the channel is changed from H 1  to H 2  and H 3  in the first and second strip symbols respectively, as shown above in  FIG. 1 . Note that channel H 2  or H 3  may be different from channel H 1  due to the change of the receive antenna. Therefore, the channel estimation of H 1  obtained in the first superslot may not be applicable for channel H 2  or H 3 . Hence, the wireless terminal uses a non-coherent demodulation protocol to decode the received signal in the strip symbols. Thus, at  508 , a signal, e.g., modulated with a non-coherent modulation scheme and having information bits spread across a frequency spectrum for one or more strip symbols, may be received. According to one example, the strip symbol(s) may comprise concatenated code, but is not limited thereto. 
   At  510 , an SNR for at least a second antenna may be estimated during a first transmission time period of the second superslot. The first transmission time period of the second superslot may correspond to, for example, one or more strip symbol durations, such as the strip symbols illustrated at the beginning of the second superslot of  FIG. 1 . A non-coherent detection protocol may be performed in the first transmission time period of the second superslot, at  512 . The non-coherent detection protocol uses only the signal received in the first transmission time period of the second superslot and does not use the signal received in any preceding time. The SNR is also estimated for the at least second antenna. The non-coherent detection protocol may be a protocol with interleaved/de-interleaved information bits as described with regard to  FIG. 4 , above. At  514 , a comparison may be made between the SNR estimated for the first antenna during the coherent detection time period and the SNR(s) detected for the at least second antenna during the non-coherent SIS detection time period. Finally, at  516 , a wireless terminal may switch to the antenna having the highest SNR based on the comparison at  514 . In this manner, a wireless terminal may be permitted to switch between multiple receive antennas as often as every superslot (e.g., 11.4 ms). 
   According to a related aspect, antenna switching may be a function of a predetermined threshold difference between antenna SNRs. For instance, the difference of SNRs at  514  may be required to exceed some predefined threshold (e.g., 0.25 dB, 0.5 dB, 1 dB, etc.) in order to justify switching between antennas. According to an example, if the predefined threshold is 0.5 dB and the first antenna has an SNR of X dB as estimated at  502 , then the SNR of a second antenna as estimated at  510  would have to meet or exceed X+0.5 dB to warrant switching from the first receive antenna to the second receive antenna. 
     FIG. 6  illustrates a methodology  600  for decoding a communication signal using an iterative SISO non-coherent demodulation protocol to demodulate and interleave concatenated code, in accordance with one or more aspects. For example, method  600  can facilitate iterative demodulation and interleaving of a received concatenated signal as described above with regard to  FIG. 4 . According to the method, a set of symbols containing a plurality of information bits may be received at  602 . The received symbol set may contain a plurality of information bits, and may be divided into a plurality of symbol subsets, each of which corresponds to an input for an inner code demodulation protocol, at  604 . A plurality of initial a priori values for inner code demodulation of the symbol subsets may be selected at  606 . At  608 , the symbol subsets may be demodulated using the initial a priori values and an inner code generator matrix to generate a plurality of first soft information values. Each of the first soft information values may be associated with one of the plurality of information bits by employing an outer code generator matrix, at  610 . At  612 , plurality of second soft information values may be calculated as an output of the outer code demodulation, where each second soft information value corresponds to one of the information bits and is calculated using at least two of the first soft information values associated with the information bit. At  614 , the second soft information values may then be utilized to determine a new set of a priori values for use in a next iteration of the inner code demodulation of the received input symbols, where the initial a priori values are replaced by the new a priori values for a subsequent iteration of method  600 , starting with demodulation at  608 . In this manner, method  600  provides an iterative series of acts that may be performed on a received strip symbol (or channel) to effectively decode the strip symbol via a low-complexity and highly efficient non-coherent SISO protocol. 
   According to related aspects, the wireless terminal may receive a signal that has been encoded using a Reed-Muller encoding technique, and may perform method  600  on the received signal. Additionally, the concatenated code received by the wireless terminal may exhibit certain properties associated with such encoding techniques. For instance, the received signal may be encoded prior to receipt by the wireless terminal using an outer code in combination with an inner code comprising at least two subblocks. Thus, it will be appreciated that method  600  facilitates performing a decoding algorithm similar to that performed by decoder  402  of  FIG. 4 . 
   According to other aspects, the set of symbols received at  602  may be divided into at least two subsets at  604 . Additionally, the inner code generator matrix employed for each subset may be the same or may be different from subset to subset. A second soft information value for a given information bit may be an average of two or more first soft information values associated with the bit. 
     FIG. 7  is an illustration of a methodology  700  for encoding a strip symbol to enable mobile antenna switching in a wireless communication environment, in accordance with various aspects. At  702 , a bit information vector may be encoded using an outer code generator matrix to generate a bit matrix, which may comprise at least two rows and any suitable number of columns. At  704 , a codeword may be generated for each row in the bit matrix by implementing an inner code generator matrix, which may comprise a Reed-Muller code but is not limited thereto. The inner code generator matrix may be the same for all rows in the bit matrix or may be different from row to row. At  706 , the codewords generated at  704  may be concatenated into a single codeword. The concatenated codeword may be mapped to a number of modulation symbols, at  708 . Modulation symbols may be mapped to a subset of tones in the strip channel at  710 . The subset of tones to which modulation symbols are mapped may be predetermined. Additionally, strip symbol tones to which modulation symbols are not mapped may be transmitted at a zero-energy level when the strip symbol is transmitted. According to an example, approximately 20% or more of the tones in the strip symbol may be transmitted at a zero-energy level. In this manner, method  700  may be utilized to facilitate performing various encoding actions, such as those described above with regard to  FIG. 1 , and any and all such actions may be performed in conjunction with method  700 . 
     FIG. 8  illustrates a system  800  that facilitates antenna switching in a wireless terminal with multiple receive antennas per receive chain, in a communication environment, in accordance with one or more aspects described herein. System  800  is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, system  800  may provide modules for performing various acts such as are described above with regard to  FIG. 1 . System  800  comprises a module for performing coherent demodulation  802  during first superslot and for estimating SNR for a first antenna. System  800  additionally comprises a module for determining whether a first superslot is ending  804  and a module for switching to a next (e.g. at least a second) antenna  806 . System  800  further comprises a module for receiving bit-interleaved, concatenated strip symbol(s)  808 , as well as a module for estimating SNR  810  for at least a second antenna and a module for performing non-coherent demodulation  812  for the at least second antenna. System  800  still further comprises a module for comparing SNRs  814  for antennas for which SNRs have been estimated, and a module for selecting an antenna  816  for receiving signal(s) during a subsequent superslot as a function of SNR comparison. It is to be understood that system  800  and the various a module comprised thereby may carryout the methods described above and/or may impart any necessary functionality to the various systems described herein. 
     FIG. 9  illustrates a system  900  that facilitates decoding concatenated-code signals received at a wireless terminal by performing an iterative soft-demodulation and interleaving algorithm, in accordance with various aspects. System  900  is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, system  900  may provide modules for performing various acts such as are described above with regard to  FIG. 4 . System  900  comprises a module for receiving  902  a set of symbols, which may have been encoded using a concatenated code, and a module  904  for dividing  904  the received set of symbols into a plurality of subsets. System  900  further comprises a module for selecting  906  an initial set of a priori values, which may be utilized by a module for demodulating  908 , in conjunction with an inner code generator matrix, to generate a first set of soft information values. System  900  further comprises a module for associating  910  each of the first soft information values with one of the plurality of information bits contained in the received set of symbols using an outer code generator matrix. A module for calculating  912  may calculate a second set of soft information values for an information bit using at least two of the first soft information values associated with the bit. A module for determining  914  may then determine a new set of a priori values as a function of the second set of soft information values, which may replace the initial set of a priori values for a next iteration of demodulating, associating, calculating, and determining by respective modules  908 ,  910 ,  912 , and  914 . It is to be understood that system  900  and the various modules comprised thereby may carryout the methods described above and/or may impart any necessary functionality to the various systems described herein. 
     FIG. 10  illustrates a system that facilitates encoding a concatenated code strip symbol that enables antenna switching by a wireless terminal in a wireless communication environment, in accordance with one or more aspects. System  1000  is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, system  1000  may provide modules for performing various acts such as are described above with regard to  FIG. 7 . System  1000  comprises a module for encoding  1002  an information bit vector with an outer code to generate a bit matrix. System  1000  further comprises a module for generating  1004  a codeword for each row in the bit matrix using an inner code generator matrix. Additionally, system  1000  may comprise a module for concatenating  1006  codewords into a single codeword. A concatenated codeword may be mapped to a number of modulation symbols by a module for mapping a concatenated codeword  1008 . Additionally, a module for mapping modulation symbols  1010  may map the modulation symbols to a subset of tones in the strip symbol. It is to be understood that system  1000  and the various modules comprised thereby may carryout the methods described above and/or may impart any necessary functionality to the various systems described herein. 
     FIG. 11  shows an exemplary communication system  1100  implemented in accordance with the present invention including multiple cells: cell  1   1102 , cell M  1104 . Note that neighboring cells  1102 ,  1104  overlap slightly, as indicated by cell boundary region  1168 , thereby providing the potential for signal interference between signals being transmitted by base stations in neighboring cells. Each cell  1102 ,  1104  of exemplary system  1100  includes three sectors. Cells which have not be subdivided into multiple sectors (N=1), cells with two sectors (N=2) and cells with more than 3 sectors (N&gt;3) are also possible in accordance with the invention. Cell  1102  includes a first sector, sector  1   1110 , a second sector, sector  2   1112 , and a third sector, sector  3   1114 . Each sector  1110 ,  1112 ,  1114  has two sector boundary regions; each boundary region is shared between two adjacent sectors. Sector boundary regions provide the potential for signal interference between signals being transmitted by base stations in neighboring sectors. Line  1116  represents a sector boundary region between sector  1   1110  and sector  2   1112 ; line  1118  represents a sector boundary region between sector  2   1112  and sector  3   1114 ; line  1120  represents a sector boundary region between sector  3   1114  and sector  1   1110 . Similarly, cell M  1104  includes a first sector, sector  1   1122 , a second sector, sector  2   1124 , and a third sector, sector  3   1126 . Line  1128  represents a sector boundary region between sector  1   1122  and sector  2   1124 ; line  1130  represents a sector boundary region between sector  2   1124  and sector  3   1126 ; line  1132  represents a boundary region between sector  3   1126  and sector  1   1122 . Cell  1   1102  includes a base station (BS), base station  1   1106 , and a plurality of end nodes (ENs) in each sector  1110 ,  1112 ,  1114 . Sector  1   1110  includes EN( 1 )  1136  and EN(X)  1138  coupled to BS  1106  via wireless links  1140 ,  1142 , respectively; sector  2   1112  includes EN( 1 ′)  1144  and EN(X′)  1146  coupled to BS  1106  via wireless links  1148 ,  1150 , respectively; sector  3   1126  includes EN( 1 ″)  1152  and EN(X″)  1154  coupled to BS  1106  via wireless links  1156 ,  1158 , respectively. Similarly, cell M  1104  includes base station M  1108 , and a plurality of end nodes (ENs) in each sector  1122 ,  1124 ,  1126 . Sector  1   1122  includes EN( 1 )  1136 ′ and EN(X)  1138 ′ coupled to BS M  1108  via wireless links  1140 ′,  1142 ′, respectively; sector  2   1124  includes EN( 1 ′)  1144 ′ and EN(X′)  1146 ′ coupled to BS M  1108  via wireless links  1148 ′,  1150 ′, respectively; sector  3   1126  includes EN( 1 ″)  1152 ′ and EN(X″)  1154 ′ coupled to BS  1108  via wireless links  1156 ′,  1158 ′, respectively. System  1100  also includes a network node  1160  which is coupled to BS 1   1106  and BS M  1108  via network links  1162 ,  1164 , respectively. Network node  1160  is also coupled to other network nodes, e.g., other base stations, AAA server nodes, intermediate nodes, routers, etc. and the Internet via network link  1166 . Network links  1162 ,  1164 ,  1166  may be, e.g., fiber optic cables. Each end node, e.g. EN  1   1136  may be a wireless terminal including a transmitter as well as a receiver. The wireless terminals, e.g., EN( 1 )  1136  may move through system  1100  and may communicate via wireless links with the base station in the cell in which the EN is currently located. The wireless terminals, (WTs), e.g. EN( 1 )  1136 , may communicate with peer nodes, e.g., other WTs in system  1100  or outside system  1100  via a base station, e.g. BS  1106 , and/or network node  1160 . WTs, e.g., EN( 1 )  1136  may be mobile communications devices such as cell phones, personal data assistants with wireless modems, etc. Each base station performs tone subset allocation using a different method for the strip-symbol periods in accordance with the invention, from the method employed for allocating tones and determining tone hopping in the rest symbol periods, e.g., non strip-symbol periods. The wireless terminals use the tone subset allocation method of the present invention along with information received from the base station, e.g., base station slope ID, sector ID information, to determine the tones that they can use to receive data and information at specific strip-symbol periods. The tone subset allocation sequence is constructed, in accordance with the invention to spread the inter-sector and inter-cell interference across each of the tones. 
     FIG. 12  illustrates an exemplary base station  1200  in accordance with the present invention. Exemplary base station  1200  implements the tone subset allocation sequences of the present invention, with different tone subset allocation sequences generated for each different sector type of the cell. The base station  1200  may be used as any one of the base stations  1126 ,  1128  of the system  1120  of  FIG. 11 . The base station  1200  includes a receiver  1202 , a transmitter  1204 , a processor  1206 , e.g., CPU, an input/output interface  1208  and memory  1210  which are coupled together by a bus  1209  over which the various elements  1202 ,  1204 ,  1206 ,  1208 , and  1210  may interchange data and information. 
   Sectorized antenna  1203  coupled to receiver  1202  is used for receiving data and other signals, e.g., channel reports, from wireless terminals transmissions from each sector within the base station&#39;s cell. Sectorized antenna  1205  coupled to transmitter  1204  is used for transmitting data and other signals, e.g., control signals, pilot signal, beacon signals, strip symbols in during a first transmission time period of a superslot, etc. to wireless terminals  1300  (see  FIG. 13 ) within each sector of the base station&#39;s cell. In various embodiments of the invention, base station  1200  may employ multiple receivers  1202  and multiple transmitters  1204 , e.g., an individual receivers  1202  for each sector and an individual transmitter  1204  for each sector. The processor  1206 , may be, e.g., a general purpose central processing unit (CPU). Processor  1206  controls operation of the base station  1200  under direction of one or more routines  1218  stored in memory  1210  and implements the methods of the present invention. I/O interface  1208  provides a connection to other network nodes, coupling the BS  1200  to other base stations, access routers, AAA server nodes, etc., other networks, and the Internet. Memory  1210  includes routines  1218  and data/information  1220 . 
   Data/information  1220  includes data  1236 , concatenation encoding information  1238  including downlink strip-symbol time information  1240  and downlink tone information  1242 , and wireless terminal (WT) data/info  1244  including a plurality of sets of WT information: WT  1  info  1246  and WT N info  1260 . Each set of WT info, e.g., WT  1  info  1246  includes data  1248 , terminal ID  1250 , sector ID  1252 , uplink channel information  1254 , downlink channel information  1256 , and mode information  1258 . 
   Routines  1218  include communications routines  1222  and base station control routines  1224 . Base station control routines  1224  includes a strip channel encoder routine, which may comprise a concatenation encoding routine  1228  that may be implemented by encoder  1214 . The concatenation encoding routine  1228  may facilitate performing encoder actions similar to those described above with regard to  FIG. 1 . 
   Data  1236  includes data to be transmitted that will be sent to encoder  1214  of transmitter  1204  for encoding prior to transmission to WTs, and received data from WTs that has been processed through decoder  1212  of receiver  1202  following reception. Downlink strip-symbol time information  1240  includes the frame synchronization structure information, such as the superslot, beaconslot, and ultraslot structure information and information specifying whether a given symbol period is a strip-symbol period, and if so, the index of the strip-symbol period and whether the strip-symbol is a resetting point to truncate the tone subset allocation sequence used by the base station. Downlink tone information  1242  includes information including a carrier frequency assigned to the base station  1200 , the number and frequency of tones, and the set of tone subsets to be allocated to the strip-symbol periods, and other cell and sector specific values such as slope, slope index and sector type. 
   Data  1248  may include data that WT 1   1300  has received from a peer node, data that WT  1   1300  desires to be transmitted to a peer node, and downlink channel quality report feedback information. Terminal ID  1250  is a base station  1200  assigned ID that identifies WT  1   1300 . Sector ID  1252  includes information identifying the sector in which WT 1   1300  is operating. Sector ID  1252  can be used, for example, to determine the sector type. Uplink channel information  1254  includes information identifying channel segments for WT 1   1300  to use, e.g., uplink traffic channel segments for data, dedicated uplink control channels for requests, power control, timing control, etc. Each uplink channel assigned to WT 1   1300  includes one or more logical tones, each logical tone following an uplink hopping sequence in accordance with the present invention. Downlink channel information  1256  includes information identifying channel segments to carry data and/or information to WT 1   1300 , e.g., downlink traffic channel segments for user data. Each downlink channel assigned to WT 1   1300  includes one or more logical tones, each following a downlink hopping sequence. Mode information  1258  includes information identifying the state of operation of WT 1   1300 , e.g. sleep, hold, on. Communications routines  1222  control the base station  1200  to perform various communications operations and implement various communications protocols. Base station control routines  1224  are used to control the base station  1200  to perform basic base station functional tasks, e.g., signal generation and reception, scheduling, and to implement the steps of the method of the present invention including transmitting signals to wireless terminals using the tone subset allocation sequences of the present invention during the strip-symbol periods. 
     FIG. 13  illustrates an exemplary wireless terminal (end node)  1300  which can be used as any one of the wireless terminals (end nodes), e.g., EN( 1 )  1136 , of the system  1100  shown in  FIG. 11 . Wireless terminal  1300  implements the tone subset allocation sequences, in accordance with the present invention. The wireless terminal  1300  includes a receiver  1302  including a decoder  1312  (e.g., which may be similar to the decoder  402  of  FIG. 4 ), a transmitter  1304  including an encoder  1314 , a processor  1306 , and memory  1308  which are coupled together by a bus  1310  over which the various elements  1302 ,  1304 ,  1306 ,  1308  can interchange data and information. An antenna  1303  used for receiving signals from a base station  1200  is coupled to receiver  1302 . An antenna  1305  used for transmitting signals, e.g., to base station  1200  is coupled to transmitter  1304 . 
   The processor  1306 , e.g., a CPU controls the operation of the wireless terminal  1300  and implements methods of the present invention by executing routines  1320  and using data/information  1322  in memory  1308 . Data/information  1322  includes user data  1334 , user information  1336 , and demodulation/interleaving information  1350 . User data  1334  may include data, intended for a peer node, which will be routed to encoder  1314  for encoding prior to transmission by transmitter  1304  to base station  1200 , and data received from the base station  1200  which has been processed by the decoder  1312  in receiver  1302 . User information  1336  includes uplink channel information  1338 , downlink channel information  1340 , terminal ID information  1342 , base station ID information  1344 , sector ID information  1346 , and mode information  1348 . Uplink channel information  1338  includes information identifying uplink channels segments that have been assigned by base station  1200  for wireless terminal  1300  to use when transmitting to the base station  1200 . Uplink channels may include uplink traffic channels, dedicated uplink control channels, e.g., request channels, power control channels and timing control channels. Each uplink channel include one or more logic tones, each logical tone following an uplink tone hopping sequence in accordance with the present invention. The uplink hopping sequences are different between each sector type of a cell and between adjacent cells. Downlink channel information  1340  includes information identifying downlink channel segments that have been assigned by base station  1200  to WT  1300  for use when BS  1200  is transmitting data/information to WT  1300 . Downlink channels may include downlink traffic channels and assignment channels, each downlink channel including one or more logical tone, each logical tone following a downlink hopping sequence, which is synchronized between each sector of the cell. 
   User info  1336  also includes terminal ID information  1342 , which is a base station  1200  assigned identification, base station ID information  1344  which identifies the specific base station  1200  that WT has established communications with, and sector ID info  1346  which identifies the specific sector of the cell where WT  1300  is presently located. Base station ID  1344  provides a cell slope value and sector ID info  1346  provides a sector index type; the cell slope value and sector index type may be used to derive the uplink tone hopping sequences in accordance with the invention. Mode information  1348  also included in user info  1336  identifies whether the WT  1300  is in sleep mode, hold mode, or on mode. 
   Demodulation/interleaving information  1350  includes downlink strip-symbol time information  1352  and downlink tone information  1354 . Downlink strip-symbol time information  1352  include the frame synchronization structure information, such as the superslot, beaconslot, and ultraslot structure information and information specifying whether a given symbol period is a strip-symbol period, and if so, the index of the strip-symbol period and whether the strip-symbol is a resetting point to truncate the tone subset allocation sequence used by the base station. Downlink tone info  1354  includes information including a carrier frequency assigned to the base station  1000 , the number and frequency of tones, and the set of tone subsets to be allocated to the strip-symbol periods, and other cell and sector specific values such as slope, slope index and sector type. 
   Routines  1320  include communications routines  1324  and wireless terminal control routines  1326 . Communications routines  1324  control the various communications protocols used by WT  1300 . Wireless terminal control routines  1326  controls basic wireless terminal  1300  functionality including the control of the receiver  1302  and transmitter  1304 . Wireless terminal control routines  1326  include an iterative decoding routine  1328 . The iterative decoding routine  1328  includes a non-coherent demodulation routine  1330  for the strip-symbol periods and an interleaving/deinterleaving routine  1332  for that facilitates decoding a received strip symbol that has been encoded using a concatenated encoding technique. 
     FIG. 14  shows an example wireless communication system  1400 . The wireless communication system  1400  depicts one base station and one user device for sake of brevity. However, it is to be appreciated that the system can include more than one base station and/or more than one user device, wherein additional base stations and/or user devices can be substantially similar or different from the exemplary base station and user device described below. In addition, it is to be appreciated that the base station and/or the user device can employ the systems and/or methods described herein. 
   Referring now to  FIG. 14 , on a downlink, at access point  1405 , a transmit (TX) data processor  1410  receives, formats, codes, interleaves, and modulates (or symbol maps) traffic data and provides modulation symbols (“data symbols”). A symbol modulator  1415  receives and processes the data symbols and pilot symbols and provides a stream of symbols. Symbol modulator  1415  multiplexes data and pilot symbols and provides them to a transmitter unit (TMTR)  1420 . Each transmit symbol may be a data symbol, a pilot symbol, or a signal value of zero. The pilot symbols may be sent continuously in each symbol period. The pilot symbols can be frequency division multiplexed (FDM), orthogonal frequency division multiplexed (OFDM), time division multiplexed (TDM), frequency division multiplexed (FDM), or code division multiplexed (CDM). 
   TMTR  1420  receives and converts the stream of symbols into one or more analog signals and further conditions (e.g., amplifies, filters, and frequency upconverts) the analog signals to generate a downlink signal suitable for transmission over the wireless channel. The downlink signal is then transmitted through an antenna  1425  to the user devices. At user device  1430 , an antenna  1435  receives the downlink signal and provides a received signal to a receiver unit (RCVR)  1440 . Receiver unit  1440  conditions (e.g., filters, amplifies, and frequency downconverts) the received signal and digitizes the conditioned signal to obtain samples. A symbol demodulator  1445  demodulates and provides received pilot symbols to a processor  1450  for channel estimation. Symbol demodulator  1445  further receives a frequency response estimate for the downlink from processor  1450 , performs data demodulation on the received data symbols to obtain data symbol estimates (which are estimates of the transmitted data symbols), and provides the data symbol estimates to an RX data processor  1455 , which demodulates (e.g., symbol demaps), deinterleaves, and decodes the data symbol estimates to recover the transmitted traffic data. The processing by symbol demodulator  1445  and RX data processor  1455  is complementary to the processing by symbol modulator  1415  and TX data processor  1410 , respectively, at access point  1405 . 
   On the uplink, a TX data processor  1460  processes traffic data and provides data symbols. A symbol modulator  1465  receives and multiplexes the data symbols with pilot symbols, performs modulation, and provides a stream of symbols. A transmitter unit  1470  then receives and processes the stream of symbols to generate an uplink signal, which is transmitted by the antenna  1435  to the access point  1405 . 
   At access point  1405 , the uplink signal from user device  1430  is received by the antenna  1425  and processed by a receiver unit  1475  to obtain samples. A symbol demodulator  1480  then processes the samples and provides received pilot symbols and data symbol estimates for the uplink. An RX data processor  1485  processes the data symbol estimates to recover the traffic data transmitted by user device  1430 . A processor  1490  performs channel estimation for each active user device transmitting on the uplink. Multiple user devices may transmit pilot concurrently on the uplink on their respective assigned sets of pilot subcarriers, where the pilot subcarrier sets may be interlaced. 
   Processors  1490  and  1450  direct (e.g., control, coordinate, manage, etc.) operation at access point  1405  and user device  1430 , respectively. Respective processors  1490  and  1450  can be associated with memory units (not shown) that store program codes and data. Processors  1490  and  1450  can utilize any of the methodologies described herein. Respective Processors  1490  and  1450  can also perform computations to derive frequency and impulse response estimates for the uplink and downlink, respectively. 
   For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art. 
   What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.