Enis Akay - Profile on Academia.edu (original) (raw)
Papers by Enis Akay
Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat fr... more Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat frequency selective channels. In our earlier work, we showed that the combination of bit interleaved coded modulation (BICM) and OFDM achieves the full frequency diversity offered by a frequency selective channel with equal power delay profile conditioned on the minimum Hamming distance, dfree, of the convolutional code. In Winter 2006, we were able to extend this result to frequency selective channels with any kind of power delay profile. This system has a simple Viterbi decoder with a modified metric.
In the Spring 2006 quarter we investigated BBO, which is a combination of BICM, single beamformin... more In the Spring 2006 quarter we investigated BBO, which is a combination of BICM, single beamforming, and OFDM. We showed that BBO achieves full diversity in space and frequency regardless of the power delay profile (PDP) of the channel. Since only one stream of data is transmitted over all transmit antennas, a simple interleaver is shown to be sufficient to achieve full space and frequency diversity. Simulation results show that beamforming-based systems introduce substantial coding gain, even with partial channel state information at the transmitter (CSIT), when compared to other systems based on space time block codes (STBC) with the same full diversity order. In addition, we show through simulations that reduction of CSIT from full resolution to only one bit per tone results in an SNR reduction of only about 1.5-2 dB.
Antennas and Wireless Propagation Letters, 2006
A multiple-input-multiple-output (MIMO) system equipped with a new class of antenna arrays, hence... more A multiple-input-multiple-output (MIMO) system equipped with a new class of antenna arrays, henceforth referred to as multifunction reconfigurable antenna arrays (MRAAs), is investigated. The elements of MRAA, i.e., multifunction reconfigurable antennas (MRAs) presented in this work are capable of dynamically changing the sense of polarization of the radiated field thereby providing two reconfigurable modes of operation, i.e., polarization diversity and space diversity. The transmission signaling scheme can also be switched between transmit diversity (TD) and spatial multiplexing (SM). The results show that the reconfigurable modes of operation of an MRAA used in conjunction with adaptive space-time modulation techniques provide additional degrees of freedom to the current adaptive MIMO systems, resulting in more robust system in terms of quality, capacity and reliability. A performance gain up to 30 dB is possible with the proposed system over conventional fixed antenna MIMO systems depending on the channel conditions.
2007 Information Theory and Applications Workshop, 2007
In this paper we analyze single beamforming in combination with bit interleaved coded modulation ... more In this paper we analyze single beamforming in combination with bit interleaved coded modulation (BICM) and OFDM. We show that BICM-Beamforming-OFDM (BBO) achieves full diversity in space and frequency independent of the power delay profile of the channel. Since only one stream of data is transmitted over all transmit antennas, a simple interleaver is shown to be sufficient to achieve full space and frequency diversity. Simulation results show that beamformingbased systems introduce substantial coding gain, even with partial channel state information at the transmitter (CSIT), when compared to other systems based on space time block codes (STBC) with the same full diversity order.
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
technique that utilizes the channel knowledge both at the transmitter and the receiver is known a... more technique that utilizes the channel knowledge both at the transmitter and the receiver is known as beamforming. Beamforming separates a MIMO channel into parallel subchannels. It was previously shown that uncoded beamforming achieves a diversity order of (N -S + 1)(M -S + 1) if S symbols are transmitted simultaneously for N transmit and M receive antennas. Hence, there is a significant drop in the diversity order (and performance) of the system with increased spatial multiplexing. In this paper, we introduce bit interleaved coded multiple beamforming and name the system BICMB. We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N, M ) and full spatial diversity of NM. Simulation results show that BICMB, due to its ability of maintaining the maximum diversity order even at full spatial multiplexing, provides substantial performance gain when compared to the best spatial multiplexing systems.
2006 Ieee 63rd Vehicular Technology Conference, May 7, 2006
Bit interleaved coded multiple beamforming (BICMB) was previously designed to achieve full spatia... more Bit interleaved coded multiple beamforming (BICMB) was previously designed to achieve full spatial multiplexing of min(N, M) and full spatial diversity of NM for N transmit and M receive antennas over flat fading channels. Furthermore, BICMB when combined with orthogonal frequency division multiplexing (OFDM) achieves full spatial multiplexing and full diversity order of NML over L-tap frequency-selective channels. BICMB requires full channel state information (CSI) both at the transmitter and receiver, however it uses uniform power and rate over the parallel channels established by multiple beamforming. In this paper, our main goal is to investigate the performance of the previously analyzed BICMB system via adaptive modulation and coding (AMC) to further utilize CSI and to improve system throughput performance. Hence, we name the new systems as Adaptive BICMB (ABICMB) over flat fading, and ABICMB-OFDM over frequency-selective channels. Simulation results show that adaptive system achieves 4-13 dB performance gain compared to non-adaptive case depending on the antenna configuration and environment. Systems analyzed require perfect CSI both at the transmitter and receiver, which may be difficult to obtain in a practical scenario. However, high performance gains achieved makes it worthwhile to study the performance of the proposed systems, leaving room for significant gain with limited feedback.
Systems and Methods for Compensating Antenna Gain Imbalance
ó In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB)... more ó In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N; M) and full spatial diversity of NM for a system with N transmit and M receive antennas. We combined BICMB with OFDM in order to combat ISI caused by
IEEE International Conference on Communications, 2005. ICC 2005. 2005, 2005
In this paper we will show and quantify both analytically and via simulations that the use of cha... more In this paper we will show and quantify both analytically and via simulations that the use of channel knowledge at the transmitter, the technique known as beamforming, achieves the maximum diversity in space when the best eigenmode is used (single beamforming). Furthermore, we will investigate beamforming in conjunction with next generation wireless local area networks (WLANs). It is known that the widely used technique in WLANs, bit interleaved coded modulation (BICM) with orthogonal frequency division multiplexing (OFDM), can achieve the maximum frequency diversity order that is inherited in the channel. We will show that the combination of BICM, single beamforming, and OFDM also leads to the maximum diversity order in space and frequency domains. In other words, for systems with N transmit and M receive antennas, BICM-Beamforming-OFDM (BBO) can achieve a diversity order of NML over L-tap frequency selective channels by using an appropriate convolutional code. In addition to having a substantial diversity order, simulation results show that beamforming and BBO introduce significant coding gains when compared to other systems based on space time block codes (STBC) with the same diversity order.
ITA Inaugural Workshop, 2006
Abstract—In this paper, we analyze the performance of bit interleaved coded multiple beamforming ... more Abstract—In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min (N, M) and full spatial diversity of NM for a system ...
IEEE Transactions on Communications, 2006
Multi-antenna communication systems have the potential to play an important role in the design of... more Multi-antenna communication systems have the potential to play an important role in the design of the next generation broadband wireless communication systems. In this paper, we study a single-user multi-antenna system with perfect channel state information (CSI) both at the transmitter and the receiver. Beamforming is used to exploit the perfect channel knowledge at both ends. We show that beamforming achieves the maximum diversity in space when only the best eigenmode is used (i.e., single beamforming). We extend our analytical results to multiple beamforming (i.e., sending more than one symbol simultaneously). Our main contribution is the analysis of the maximum achievable diversity order of beamforming systems.
… and Propagation Society …, 2006
A MIMO system equipped with a new class of antenna arrays, henceforth referred to as multifunctio... more A MIMO system equipped with a new class of antenna arrays, henceforth referred to as multifunction reconfigurable antenna arrays (MRAAs), is investigated. The elements of MRAA, i.e. MRAs presented in this work are capable of dynamically changing the sense of polarization of the radiated field thereby providing two reconfigurable modes of operation, i.e. polarization diversity and space diversity. The transmission signaling scheme can also be switched between transmit diversity (TD) and spatial multiplexing (SM). The results show that the reconfigurable modes of operation of an MRAA used in conjunction with adaptive space-time modulation techniques provide additional degree of freedoms to the current adaptive MIMO systems, thereby resulting in more robust system in terms of quality, capacity and reliability. A substantial performance gain is achievable with the proposed system over conventional fixed antenna MIMO systems depending on the channel conditions.
IEEE Transactions on Communications, 2000
In this paper, we investigate the performance of bit interleaved coded multiple beamforming (BICM... more In this paper, we investigate the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that BICMB achieves full spatial multiplexing of min(N, M ) and full spatial diversity of N M with N transmit and M receive antennas over quasi-static Rayleigh flat fading channels.
Multi-input multi-output wireless systems with maximum diversity and spatial multiplexing
Abstract: In this dissertation we show that BICM-OFDM systems can achieve the maximum frequency d... more Abstract: In this dissertation we show that BICM-OFDM systems can achieve the maximum frequency diversity regardless of the power delay profile (PDP) of the frequency selective channel. That is for L-tap frequency selective channels, BICM-OFDM is shown to achieve ...
Ieee Transactions on Communications, Dec 1, 2006
Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat fr... more Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat frequency selective channels. In this paper we show that the combination of bit interleaved coded modulation (BICM) and OFDM achieves the full frequency diversity offered by a frequency selective channel with any kind of power delay profile, conditioned on the minimum Hamming distance, d f ree , of the convolutional code. This system has a simple Viterbi decoder with a modified metric. We then show that by combining such a system with space time block coding (STBC), one can achieve the full space and frequency diversity of a frequency selective channel with N transmit and M receive antennas. BICM-STBC-OFDM achieves the maximum diversity order of N M L over L-tap frequency selective channels regardless of the power delay profile of the channel. This latter system also has a simple Viterbi decoder with a properly modified metric. We verify our analytical results via simulations, including channels employed in the IEEE 802.11 standards.
The interleaver design criteria described in [1] should take into account all error patterns of i... more The interleaver design criteria described in [1] should take into account all error patterns of interest.
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayle... more It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayleigh fading channel by bit-wise interleaving at the encoder output, and by using an appropriate soft-decision metric for a Viterbi decoder at the receiver. Caire et al presented the details of the theory behind bit-interleaved coded modulation (BICM).
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004
It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayle... more It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayleigh fading channel by bit-wise interleaving at the encoder output, and by using an appropriate soft-decision metric for a Viterbi decoder at the receiver. Caire et al presented the details of the theory behind bit-interleaved coded modulation (BICM).
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004
It is well-known that, for systems that deploy conventional convolutional codes, a Viterbi decode... more It is well-known that, for systems that deploy conventional convolutional codes, a Viterbi decoder is the best solution in maximum likelihood sense to decode an information sequence. Typically, a Viterbi decoder uses Euclidean or Hamming distance as a metric. The use of a conventional metric leads to a high performance for systems that are employed for frequency nonselective channels (e.g., additive white Gaussian noise (AWGN), or Rayleigh fading). However, if the system is based on orthogonal frequency division multiplexing (OFDM) and the channel has frequency selective multipath fading, then the performance can be further improved. In this paper we propose a simple modification to the conventional Viterbi metric (Euclidean distance) that improves the performance substantially if the channel is frequency selective. Simulation results on wireless local area network (WLAN) standard IEEE 802.11a show that the performance is improved about 10 dB when the proposed metric is used. Furthermore, the proposed metric gives the same high performance as the conventional Viterbi metric if the channel is AWGN or flat fading.
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
It is well-known that using multiple antennas provides a substantial capacity and diversity incre... more It is well-known that using multiple antennas provides a substantial capacity and diversity increase for wireless communication systems. A multi-input multi-output (MIMO) technique that utilizes the channel knowledge both at the transmitter and the receiver is known as beamforming. Beamforming separates a MIMO channel into parallel subchannels. It was previously shown that uncoded beamforming achieves a diversity order of (N − S + 1)(M − S + 1) if S symbols are transmitted simultaneously for N transmit and M receive antennas. Hence, there is a significant drop in the diversity order (and performance) of the system with increased spatial multiplexing. In this paper, we introduce bit interleaved coded multiple beamforming and name the system BICMB. We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N, M ) and full spatial diversity of NM. Simulation results show that BICMB, due to its ability of maintaining the maximum diversity order even at full spatial multiplexing, provides substantial performance gain when compared to the best spatial multiplexing systems.
Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat fr... more Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat frequency selective channels. In our earlier work, we showed that the combination of bit interleaved coded modulation (BICM) and OFDM achieves the full frequency diversity offered by a frequency selective channel with equal power delay profile conditioned on the minimum Hamming distance, dfree, of the convolutional code. In Winter 2006, we were able to extend this result to frequency selective channels with any kind of power delay profile. This system has a simple Viterbi decoder with a modified metric.
In the Spring 2006 quarter we investigated BBO, which is a combination of BICM, single beamformin... more In the Spring 2006 quarter we investigated BBO, which is a combination of BICM, single beamforming, and OFDM. We showed that BBO achieves full diversity in space and frequency regardless of the power delay profile (PDP) of the channel. Since only one stream of data is transmitted over all transmit antennas, a simple interleaver is shown to be sufficient to achieve full space and frequency diversity. Simulation results show that beamforming-based systems introduce substantial coding gain, even with partial channel state information at the transmitter (CSIT), when compared to other systems based on space time block codes (STBC) with the same full diversity order. In addition, we show through simulations that reduction of CSIT from full resolution to only one bit per tone results in an SNR reduction of only about 1.5-2 dB.
Antennas and Wireless Propagation Letters, 2006
A multiple-input-multiple-output (MIMO) system equipped with a new class of antenna arrays, hence... more A multiple-input-multiple-output (MIMO) system equipped with a new class of antenna arrays, henceforth referred to as multifunction reconfigurable antenna arrays (MRAAs), is investigated. The elements of MRAA, i.e., multifunction reconfigurable antennas (MRAs) presented in this work are capable of dynamically changing the sense of polarization of the radiated field thereby providing two reconfigurable modes of operation, i.e., polarization diversity and space diversity. The transmission signaling scheme can also be switched between transmit diversity (TD) and spatial multiplexing (SM). The results show that the reconfigurable modes of operation of an MRAA used in conjunction with adaptive space-time modulation techniques provide additional degrees of freedom to the current adaptive MIMO systems, resulting in more robust system in terms of quality, capacity and reliability. A performance gain up to 30 dB is possible with the proposed system over conventional fixed antenna MIMO systems depending on the channel conditions.
2007 Information Theory and Applications Workshop, 2007
In this paper we analyze single beamforming in combination with bit interleaved coded modulation ... more In this paper we analyze single beamforming in combination with bit interleaved coded modulation (BICM) and OFDM. We show that BICM-Beamforming-OFDM (BBO) achieves full diversity in space and frequency independent of the power delay profile of the channel. Since only one stream of data is transmitted over all transmit antennas, a simple interleaver is shown to be sufficient to achieve full space and frequency diversity. Simulation results show that beamformingbased systems introduce substantial coding gain, even with partial channel state information at the transmitter (CSIT), when compared to other systems based on space time block codes (STBC) with the same full diversity order.
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
technique that utilizes the channel knowledge both at the transmitter and the receiver is known a... more technique that utilizes the channel knowledge both at the transmitter and the receiver is known as beamforming. Beamforming separates a MIMO channel into parallel subchannels. It was previously shown that uncoded beamforming achieves a diversity order of (N -S + 1)(M -S + 1) if S symbols are transmitted simultaneously for N transmit and M receive antennas. Hence, there is a significant drop in the diversity order (and performance) of the system with increased spatial multiplexing. In this paper, we introduce bit interleaved coded multiple beamforming and name the system BICMB. We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N, M ) and full spatial diversity of NM. Simulation results show that BICMB, due to its ability of maintaining the maximum diversity order even at full spatial multiplexing, provides substantial performance gain when compared to the best spatial multiplexing systems.
2006 Ieee 63rd Vehicular Technology Conference, May 7, 2006
Bit interleaved coded multiple beamforming (BICMB) was previously designed to achieve full spatia... more Bit interleaved coded multiple beamforming (BICMB) was previously designed to achieve full spatial multiplexing of min(N, M) and full spatial diversity of NM for N transmit and M receive antennas over flat fading channels. Furthermore, BICMB when combined with orthogonal frequency division multiplexing (OFDM) achieves full spatial multiplexing and full diversity order of NML over L-tap frequency-selective channels. BICMB requires full channel state information (CSI) both at the transmitter and receiver, however it uses uniform power and rate over the parallel channels established by multiple beamforming. In this paper, our main goal is to investigate the performance of the previously analyzed BICMB system via adaptive modulation and coding (AMC) to further utilize CSI and to improve system throughput performance. Hence, we name the new systems as Adaptive BICMB (ABICMB) over flat fading, and ABICMB-OFDM over frequency-selective channels. Simulation results show that adaptive system achieves 4-13 dB performance gain compared to non-adaptive case depending on the antenna configuration and environment. Systems analyzed require perfect CSI both at the transmitter and receiver, which may be difficult to obtain in a practical scenario. However, high performance gains achieved makes it worthwhile to study the performance of the proposed systems, leaving room for significant gain with limited feedback.
Systems and Methods for Compensating Antenna Gain Imbalance
ó In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB)... more ó In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N; M) and full spatial diversity of NM for a system with N transmit and M receive antennas. We combined BICMB with OFDM in order to combat ISI caused by
IEEE International Conference on Communications, 2005. ICC 2005. 2005, 2005
In this paper we will show and quantify both analytically and via simulations that the use of cha... more In this paper we will show and quantify both analytically and via simulations that the use of channel knowledge at the transmitter, the technique known as beamforming, achieves the maximum diversity in space when the best eigenmode is used (single beamforming). Furthermore, we will investigate beamforming in conjunction with next generation wireless local area networks (WLANs). It is known that the widely used technique in WLANs, bit interleaved coded modulation (BICM) with orthogonal frequency division multiplexing (OFDM), can achieve the maximum frequency diversity order that is inherited in the channel. We will show that the combination of BICM, single beamforming, and OFDM also leads to the maximum diversity order in space and frequency domains. In other words, for systems with N transmit and M receive antennas, BICM-Beamforming-OFDM (BBO) can achieve a diversity order of NML over L-tap frequency selective channels by using an appropriate convolutional code. In addition to having a substantial diversity order, simulation results show that beamforming and BBO introduce significant coding gains when compared to other systems based on space time block codes (STBC) with the same diversity order.
ITA Inaugural Workshop, 2006
Abstract—In this paper, we analyze the performance of bit interleaved coded multiple beamforming ... more Abstract—In this paper, we analyze the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min (N, M) and full spatial diversity of NM for a system ...
IEEE Transactions on Communications, 2006
Multi-antenna communication systems have the potential to play an important role in the design of... more Multi-antenna communication systems have the potential to play an important role in the design of the next generation broadband wireless communication systems. In this paper, we study a single-user multi-antenna system with perfect channel state information (CSI) both at the transmitter and the receiver. Beamforming is used to exploit the perfect channel knowledge at both ends. We show that beamforming achieves the maximum diversity in space when only the best eigenmode is used (i.e., single beamforming). We extend our analytical results to multiple beamforming (i.e., sending more than one symbol simultaneously). Our main contribution is the analysis of the maximum achievable diversity order of beamforming systems.
… and Propagation Society …, 2006
A MIMO system equipped with a new class of antenna arrays, henceforth referred to as multifunctio... more A MIMO system equipped with a new class of antenna arrays, henceforth referred to as multifunction reconfigurable antenna arrays (MRAAs), is investigated. The elements of MRAA, i.e. MRAs presented in this work are capable of dynamically changing the sense of polarization of the radiated field thereby providing two reconfigurable modes of operation, i.e. polarization diversity and space diversity. The transmission signaling scheme can also be switched between transmit diversity (TD) and spatial multiplexing (SM). The results show that the reconfigurable modes of operation of an MRAA used in conjunction with adaptive space-time modulation techniques provide additional degree of freedoms to the current adaptive MIMO systems, thereby resulting in more robust system in terms of quality, capacity and reliability. A substantial performance gain is achievable with the proposed system over conventional fixed antenna MIMO systems depending on the channel conditions.
IEEE Transactions on Communications, 2000
In this paper, we investigate the performance of bit interleaved coded multiple beamforming (BICM... more In this paper, we investigate the performance of bit interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that BICMB achieves full spatial multiplexing of min(N, M ) and full spatial diversity of N M with N transmit and M receive antennas over quasi-static Rayleigh flat fading channels.
Multi-input multi-output wireless systems with maximum diversity and spatial multiplexing
Abstract: In this dissertation we show that BICM-OFDM systems can achieve the maximum frequency d... more Abstract: In this dissertation we show that BICM-OFDM systems can achieve the maximum frequency diversity regardless of the power delay profile (PDP) of the frequency selective channel. That is for L-tap frequency selective channels, BICM-OFDM is shown to achieve ...
Ieee Transactions on Communications, Dec 1, 2006
Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat fr... more Orthogonal frequency division multiplexing (OFDM) is known as an efficient technique to combat frequency selective channels. In this paper we show that the combination of bit interleaved coded modulation (BICM) and OFDM achieves the full frequency diversity offered by a frequency selective channel with any kind of power delay profile, conditioned on the minimum Hamming distance, d f ree , of the convolutional code. This system has a simple Viterbi decoder with a modified metric. We then show that by combining such a system with space time block coding (STBC), one can achieve the full space and frequency diversity of a frequency selective channel with N transmit and M receive antennas. BICM-STBC-OFDM achieves the maximum diversity order of N M L over L-tap frequency selective channels regardless of the power delay profile of the channel. This latter system also has a simple Viterbi decoder with a properly modified metric. We verify our analytical results via simulations, including channels employed in the IEEE 802.11 standards.
The interleaver design criteria described in [1] should take into account all error patterns of i... more The interleaver design criteria described in [1] should take into account all error patterns of interest.
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayle... more It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayleigh fading channel by bit-wise interleaving at the encoder output, and by using an appropriate soft-decision metric for a Viterbi decoder at the receiver. Caire et al presented the details of the theory behind bit-interleaved coded modulation (BICM).
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004
It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayle... more It has been shown by Zehavi that the performance of coded modulation can be improved over a Rayleigh fading channel by bit-wise interleaving at the encoder output, and by using an appropriate soft-decision metric for a Viterbi decoder at the receiver. Caire et al presented the details of the theory behind bit-interleaved coded modulation (BICM).
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004
It is well-known that, for systems that deploy conventional convolutional codes, a Viterbi decode... more It is well-known that, for systems that deploy conventional convolutional codes, a Viterbi decoder is the best solution in maximum likelihood sense to decode an information sequence. Typically, a Viterbi decoder uses Euclidean or Hamming distance as a metric. The use of a conventional metric leads to a high performance for systems that are employed for frequency nonselective channels (e.g., additive white Gaussian noise (AWGN), or Rayleigh fading). However, if the system is based on orthogonal frequency division multiplexing (OFDM) and the channel has frequency selective multipath fading, then the performance can be further improved. In this paper we propose a simple modification to the conventional Viterbi metric (Euclidean distance) that improves the performance substantially if the channel is frequency selective. Simulation results on wireless local area network (WLAN) standard IEEE 802.11a show that the performance is improved about 10 dB when the proposed metric is used. Furthermore, the proposed metric gives the same high performance as the conventional Viterbi metric if the channel is AWGN or flat fading.
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
It is well-known that using multiple antennas provides a substantial capacity and diversity incre... more It is well-known that using multiple antennas provides a substantial capacity and diversity increase for wireless communication systems. A multi-input multi-output (MIMO) technique that utilizes the channel knowledge both at the transmitter and the receiver is known as beamforming. Beamforming separates a MIMO channel into parallel subchannels. It was previously shown that uncoded beamforming achieves a diversity order of (N − S + 1)(M − S + 1) if S symbols are transmitted simultaneously for N transmit and M receive antennas. Hence, there is a significant drop in the diversity order (and performance) of the system with increased spatial multiplexing. In this paper, we introduce bit interleaved coded multiple beamforming and name the system BICMB. We provide interleaver design criteria such that the resulting system achieves full spatial multiplexing of min(N, M ) and full spatial diversity of NM. Simulation results show that BICMB, due to its ability of maintaining the maximum diversity order even at full spatial multiplexing, provides substantial performance gain when compared to the best spatial multiplexing systems.