This letter presents an iterative layered space-time (LST) receiver structure for single-carrier ... more This letter presents an iterative layered space-time (LST) receiver structure for single-carrier (SC)-based transmission in severe time-dispersive channels. The proposed receiver combines LST principles with iterative block decision feedback equalization (IB-DFE) techniques.
ABSTRACT Block transmission techniques, with appropriate cyclic prefix and frequency-domain proce... more ABSTRACT Block transmission techniques, with appropriate cyclic prefix and frequency-domain processing schemes, have been shown to be excellent candidates for digital transmission over severely time-dispersive channels, allowing good performance with implementation complexity that is much lower than traditional time-domain processing schemes. Orthogonal frequency-division multiplexing (OFDM) modulation is the most popular block transmission technique. Single-carrier (SC) modulation using frequency-domain equalization (FDE) is an attractive alternative approach based on this principle. In this paper, we propose two new receiver structures for multiple-input-multiple-output (MIMO) channels employing SC (MIMO-SC) modulation and FDE schemes. These receivers have a hybrid structure with frequency-domain feedforward and time-domain feedback filters for intersymbol interference (ISI) and interference cancellation. The proposed schemes are compared with different MIMO systems employing OFDM modulation (MIMO-OFDM) receivers in terms of performance [bit error rate (BER) and throughput] and complexity. Our performance results show the superiority of MIMO-SC approaches relative to MIMO-OFDM in terms of the BER performance for the simulated scenarios. Also, the simulation results show that the proposed hybrid MIMO-SC receivers yield a higher throughput than a MIMO-OFDM system.
Single-carrier transmission is one of the most potential options for uplink transmission in wide-... more Single-carrier transmission is one of the most potential options for uplink transmission in wide-area deployments. It combines the benefits of computationally simple transmitter processing and highly efficient power amplification at the terminal. Frequency-domain methods for efficient equalization can be utilized at the access point either in linear MMSE equalization or in iterative turbo equalization. We describe the potential solutions in
A PHY is proposed for 802.16.3 in which modulation format and coding rate can be adjusted on a bl... more A PHY is proposed for 802.16.3 in which modulation format and coding rate can be adjusted on a block by block basis to provide optimum channel utilization for the widest range of channel conditions.
The authors investigate the performance of a decision-feedback equalizer in the presence of co-ch... more The authors investigate the performance of a decision-feedback equalizer in the presence of co-channel interference. Through ideal calculations and simulations under static channel conditions, they show that a DFE is capable of achieving significantly better performance in the presence of CCI than in an equal amount of noise. Furthermore, they observe that DFE performance in the presence of co-channel interference
[Proceedings] GLOBECOM '90: IEEE Global Telecommunications Conference and Exhibition, 1990
Optimum baseband combining with coherent BPSK (binary phase-shift keying) or QPSK (quadrature pha... more Optimum baseband combining with coherent BPSK (binary phase-shift keying) or QPSK (quadrature phase-shift keying) is an attractive technique for wideband TDMA (time-division multiple-access) portable communication radio links in view of its ability not only to combat dispersive fading but also to cancel cochannel interference. The performance of such a scheme is investigated for data rates ranging from 1 to 20
GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 2001
This paper provides a theoretical characterization of the multihop wireless communications channe... more This paper provides a theoretical characterization of the multihop wireless communications channel without diversity, wherein intermediate terminals relay information without employing spatial diversity techniques. Two channel models are proposed and developed: one where each intermediate terminal digitally decodes and re-encodes the received signal from the immediately preceding terminal and the other where each intermediate terminal simply amplifies the received signal from the immediately preceding terminal. These models are compared, through analysis and simulations, with the singlehop reference channel on the basis of probability of outage and probability of error. Both models achieve significant gains over the singlehop reference channel, with the amplified relaying model matching the performance of the decoded relaying model despite noise propagation.
A family of orthogonal/convolutional codes for mobile CDMA communications is discussed. Their des... more A family of orthogonal/convolutional codes for mobile CDMA communications is discussed. Their design and implementational aspects are discussed. The R0 parameter of this family of codes is analyzed and presented in a uniform format. It is shown that it is desirable to use a code with a higher mobile CDMA communications. Simulation results are given. In particular, the authors simulated
IEEE Global Telecommunications Conference, 2004. GLOBECOM '04., 2004
In this paper we present a multiple access scheme for the up-link of broadband wireless systems. ... more In this paper we present a multiple access scheme for the up-link of broadband wireless systems. We consider SC-based (Single Carrier) block transmission, with all users transmitting continuously, regardless of their data-rate. The transmitted signals can have very low ...
IEEE Global Telecommunications Conference, 2004. GLOBECOM '04., 2004
The concept of relaying is a promising solution for the challenging throughput and high data rate... more The concept of relaying is a promising solution for the challenging throughput and high data rate coverage requirements of future wireless cellular networks. In this paper, we demonstrate that the area that a single BS (base station) can provide high data rate coverage can significantly be increased by the employment of digital fixed relays (deployed by the service provider) without any penalty in capacity. This network architecture which allows two-hop links (when necessary) is expected to facilitate cost-efficient high data rate coverage in beyond-3G cellular wireless networks. In particular we considered the downlink of a non-CDMA network where 6 digital fixed relays are placed around each BS in a hexagonal layout. A user equipment (UE) chooses to receive the transmitted signal either directly (in single hop) from the BS or via one of the relays (in two hops). Whenever a relay is used, a second channel is needed as the relays cannot receive and transmit at the same channel. We propose a "pre-configured" relaying channel selection algorithm which incurs minimal overhead due to its fixed nature. In this algorithm, relays further reuse the already used channels in the network; but this reusing is done in a controlled manner in order to prevent the co-channel interference from increasing to unacceptable levels. Therefore, the benefits of relaying are achieved without any loss in capacity (bandwidth). The improved two-hop links are exploited to yield higher throughput through the use of adaptive modulation and coding. We consistently observed that the throughput is increased and the outage is decreased in the relay-augmented network, which is converted to range extension without any capacity penalty, for the realistic range of values of the propagation and other system parameters investigated.
Abstract— A low complexity frequency domain iterative decision-directed channel estimation (FD-ID... more Abstract— A low complexity frequency domain iterative decision-directed channel estimation (FD-IDDCE) technique for single-carrier (SC) systems with frequency domain multiplexed (FDM) pilots is proposed. The tentative hard decisions from either the frequency domain ...
= Digital relaying is a technique that uses certain mobile terminals that have good communicatio... more = Digital relaying is a technique that uses certain mobile terminals that have good communication links with the base station to act as relay nodes for those that do not have. With this technique, the signal quality at the destination is expected to improve since the signal only goes through favorable links and, at each intermediate node, the signal is decoded and re-encoded (so that no noise is propagated) before forwarding. One of the major costs of relaying is that additional channels are needed. In this paper, we investigated the effect of using different schemes for selecting channels -among those already used in the adjacent cells -for relaying on performance improvement. Our simulation results show that not only can relaying improve the performance; but also, with power control this improvement is quite insensitive to the channel selection scheme. Furthermore, with small cell radii where there is a potential for high interference level, only a low relay node transmit power is sufficient to improve the system performance significantly.
 We consider a TDMA cellular multihop network where relaying -via wireless terminals that have a... more  We consider a TDMA cellular multihop network where relaying -via wireless terminals that have a good communication link to the base station -is used as a coverage enhancement technique. Provided that the subscriber density is not very low, relaying vi a wireless terminals can have a significant impact on coverage, capacity, and throughput. This is mainly due to the fact that the signals only have to travel through shorter distances and/or improved paths. In this work, we investigated the effects of relaying node selection strategies (essentially a routing issue) and maximum relayer transmit power level on coverage. Our simulation results show that with a very modest level of relaying node transmit power and with some moderate intelligence incorporated i n the relaying node selection scheme, the (high data rate) coverage can be improved significantly through two-hop relaying without consuming any additional bandwidth.
Absfruct -To reduce the echo canceler complexity associated with the cancellations of subscriber ... more Absfruct -To reduce the echo canceler complexity associated with the cancellations of subscriber loop echo responses with long tails, we propose and investigate a hvo-stage digital echo canceler, in which the second stage is an adaptively weighted combination of orthonormal IIR responses. Satisfactory performance (70-dB cancellation) was found for a variety of loops at 80 and 320 kbaud symbol rates with 15 such IIR responses, based on Laguerre functions. The first echo canceler stage is a conventional transversal filter with 20-40 tap coefficients. Substantial complexity reduction was achieved by the new structure. Adaptation convergence was also analyzed and simulated.
Proceedings of 1997 Wireless Communications Conference, 1997
Abstract This paper reports on the work performed on the broadband indoor 29.5-GHz radio channel ... more Abstract This paper reports on the work performed on the broadband indoor 29.5-GHz radio channel measurements employing a directional-to-directional antenna configuration. The use of a programmable array antenna at the receiver allows investigations of the channel behavior for various reception angles. The reported results include the channel delay spread properties, the angle-dependent received power, and the correlation of two signals of different reception directions
Canadian Conference on Electrical and Computer Engineering 2004 (IEEE Cat. No.04CH37513), 2004
Augmentation of the conventional cellular networks with wireless fixed relays, to enable multi-ho... more Augmentation of the conventional cellular networks with wireless fixed relays, to enable multi-hop communications, is being considered for beyond-3G cellular networks in order to provide high data rate coverage in a cost-effective manner. In this paper, we consider a Cellular Relay Network (CRN) where a large number of low-complexity/low-power wireless fixed relays are deployed around the central node (equivalent of a BS) in each cell. Each relay and central node covers only a small area with a small amount of power, enabling the reuse of the frequency-time resources. The contribution of this paper is to evaluate the cell capacity (i.e., aggregate throughput) in the CRN which enables to make comparisons between the cell capacities of the CRN and the conventional cellular network. The paper shows that the cell capacity of the CRN does not depend on the cell size or the total number of relays in the cell, but it rather depends on the number of nearest relays to the central node.
In this paper, we consider the uplink of SC-based (single-carrier) block transmission systems whe... more In this paper, we consider the uplink of SC-based (single-carrier) block transmission systems where the transmission bandwidth associated to each channel, exceeds the symbol rate and we can have significant overlapping between adjacent channels. We present an iterative frequency-domain receiver for joint equalization and ACI (adjacent channel interference) suppression taking advantage of spectral correlations for the separation of cyclostationary signals.
A new PHASE algorithm is proposed for blind adaptive extraction of signal in the presence of inte... more A new PHASE algorithm is proposed for blind adaptive extraction of signal in the presence of interference by cyclostationary signal processing using an antenna array. The algorithm operates in an interference-limited system in which the desired and interfering signals have equal symbol rates, but slightly different carrier frequencies. Compared to the SCORE algorithm and a modified version of SCORE, the
The paper concerns the feasibility and achievable performance of adaptive filtering in an interfe... more The paper concerns the feasibility and achievable performance of adaptive filtering in an interference-limited multipath fading environment as encountered in indoor wireless communications. In a typical cellular radio application, the performance-limiting impairment is interference due to synchronous data streams from other co-channel and adjacent channel users (CCI and ACI). The receiver under consideration employs an adaptive fractionally spaced decision feedback
This letter presents an iterative layered space-time (LST) receiver structure for single-carrier ... more This letter presents an iterative layered space-time (LST) receiver structure for single-carrier (SC)-based transmission in severe time-dispersive channels. The proposed receiver combines LST principles with iterative block decision feedback equalization (IB-DFE) techniques.
ABSTRACT Block transmission techniques, with appropriate cyclic prefix and frequency-domain proce... more ABSTRACT Block transmission techniques, with appropriate cyclic prefix and frequency-domain processing schemes, have been shown to be excellent candidates for digital transmission over severely time-dispersive channels, allowing good performance with implementation complexity that is much lower than traditional time-domain processing schemes. Orthogonal frequency-division multiplexing (OFDM) modulation is the most popular block transmission technique. Single-carrier (SC) modulation using frequency-domain equalization (FDE) is an attractive alternative approach based on this principle. In this paper, we propose two new receiver structures for multiple-input-multiple-output (MIMO) channels employing SC (MIMO-SC) modulation and FDE schemes. These receivers have a hybrid structure with frequency-domain feedforward and time-domain feedback filters for intersymbol interference (ISI) and interference cancellation. The proposed schemes are compared with different MIMO systems employing OFDM modulation (MIMO-OFDM) receivers in terms of performance [bit error rate (BER) and throughput] and complexity. Our performance results show the superiority of MIMO-SC approaches relative to MIMO-OFDM in terms of the BER performance for the simulated scenarios. Also, the simulation results show that the proposed hybrid MIMO-SC receivers yield a higher throughput than a MIMO-OFDM system.
Single-carrier transmission is one of the most potential options for uplink transmission in wide-... more Single-carrier transmission is one of the most potential options for uplink transmission in wide-area deployments. It combines the benefits of computationally simple transmitter processing and highly efficient power amplification at the terminal. Frequency-domain methods for efficient equalization can be utilized at the access point either in linear MMSE equalization or in iterative turbo equalization. We describe the potential solutions in
A PHY is proposed for 802.16.3 in which modulation format and coding rate can be adjusted on a bl... more A PHY is proposed for 802.16.3 in which modulation format and coding rate can be adjusted on a block by block basis to provide optimum channel utilization for the widest range of channel conditions.
The authors investigate the performance of a decision-feedback equalizer in the presence of co-ch... more The authors investigate the performance of a decision-feedback equalizer in the presence of co-channel interference. Through ideal calculations and simulations under static channel conditions, they show that a DFE is capable of achieving significantly better performance in the presence of CCI than in an equal amount of noise. Furthermore, they observe that DFE performance in the presence of co-channel interference
[Proceedings] GLOBECOM '90: IEEE Global Telecommunications Conference and Exhibition, 1990
Optimum baseband combining with coherent BPSK (binary phase-shift keying) or QPSK (quadrature pha... more Optimum baseband combining with coherent BPSK (binary phase-shift keying) or QPSK (quadrature phase-shift keying) is an attractive technique for wideband TDMA (time-division multiple-access) portable communication radio links in view of its ability not only to combat dispersive fading but also to cancel cochannel interference. The performance of such a scheme is investigated for data rates ranging from 1 to 20
GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 2001
This paper provides a theoretical characterization of the multihop wireless communications channe... more This paper provides a theoretical characterization of the multihop wireless communications channel without diversity, wherein intermediate terminals relay information without employing spatial diversity techniques. Two channel models are proposed and developed: one where each intermediate terminal digitally decodes and re-encodes the received signal from the immediately preceding terminal and the other where each intermediate terminal simply amplifies the received signal from the immediately preceding terminal. These models are compared, through analysis and simulations, with the singlehop reference channel on the basis of probability of outage and probability of error. Both models achieve significant gains over the singlehop reference channel, with the amplified relaying model matching the performance of the decoded relaying model despite noise propagation.
A family of orthogonal/convolutional codes for mobile CDMA communications is discussed. Their des... more A family of orthogonal/convolutional codes for mobile CDMA communications is discussed. Their design and implementational aspects are discussed. The R0 parameter of this family of codes is analyzed and presented in a uniform format. It is shown that it is desirable to use a code with a higher mobile CDMA communications. Simulation results are given. In particular, the authors simulated
IEEE Global Telecommunications Conference, 2004. GLOBECOM '04., 2004
In this paper we present a multiple access scheme for the up-link of broadband wireless systems. ... more In this paper we present a multiple access scheme for the up-link of broadband wireless systems. We consider SC-based (Single Carrier) block transmission, with all users transmitting continuously, regardless of their data-rate. The transmitted signals can have very low ...
IEEE Global Telecommunications Conference, 2004. GLOBECOM '04., 2004
The concept of relaying is a promising solution for the challenging throughput and high data rate... more The concept of relaying is a promising solution for the challenging throughput and high data rate coverage requirements of future wireless cellular networks. In this paper, we demonstrate that the area that a single BS (base station) can provide high data rate coverage can significantly be increased by the employment of digital fixed relays (deployed by the service provider) without any penalty in capacity. This network architecture which allows two-hop links (when necessary) is expected to facilitate cost-efficient high data rate coverage in beyond-3G cellular wireless networks. In particular we considered the downlink of a non-CDMA network where 6 digital fixed relays are placed around each BS in a hexagonal layout. A user equipment (UE) chooses to receive the transmitted signal either directly (in single hop) from the BS or via one of the relays (in two hops). Whenever a relay is used, a second channel is needed as the relays cannot receive and transmit at the same channel. We propose a "pre-configured" relaying channel selection algorithm which incurs minimal overhead due to its fixed nature. In this algorithm, relays further reuse the already used channels in the network; but this reusing is done in a controlled manner in order to prevent the co-channel interference from increasing to unacceptable levels. Therefore, the benefits of relaying are achieved without any loss in capacity (bandwidth). The improved two-hop links are exploited to yield higher throughput through the use of adaptive modulation and coding. We consistently observed that the throughput is increased and the outage is decreased in the relay-augmented network, which is converted to range extension without any capacity penalty, for the realistic range of values of the propagation and other system parameters investigated.
Abstract— A low complexity frequency domain iterative decision-directed channel estimation (FD-ID... more Abstract— A low complexity frequency domain iterative decision-directed channel estimation (FD-IDDCE) technique for single-carrier (SC) systems with frequency domain multiplexed (FDM) pilots is proposed. The tentative hard decisions from either the frequency domain ...
= Digital relaying is a technique that uses certain mobile terminals that have good communicatio... more = Digital relaying is a technique that uses certain mobile terminals that have good communication links with the base station to act as relay nodes for those that do not have. With this technique, the signal quality at the destination is expected to improve since the signal only goes through favorable links and, at each intermediate node, the signal is decoded and re-encoded (so that no noise is propagated) before forwarding. One of the major costs of relaying is that additional channels are needed. In this paper, we investigated the effect of using different schemes for selecting channels -among those already used in the adjacent cells -for relaying on performance improvement. Our simulation results show that not only can relaying improve the performance; but also, with power control this improvement is quite insensitive to the channel selection scheme. Furthermore, with small cell radii where there is a potential for high interference level, only a low relay node transmit power is sufficient to improve the system performance significantly.
 We consider a TDMA cellular multihop network where relaying -via wireless terminals that have a... more  We consider a TDMA cellular multihop network where relaying -via wireless terminals that have a good communication link to the base station -is used as a coverage enhancement technique. Provided that the subscriber density is not very low, relaying vi a wireless terminals can have a significant impact on coverage, capacity, and throughput. This is mainly due to the fact that the signals only have to travel through shorter distances and/or improved paths. In this work, we investigated the effects of relaying node selection strategies (essentially a routing issue) and maximum relayer transmit power level on coverage. Our simulation results show that with a very modest level of relaying node transmit power and with some moderate intelligence incorporated i n the relaying node selection scheme, the (high data rate) coverage can be improved significantly through two-hop relaying without consuming any additional bandwidth.
Absfruct -To reduce the echo canceler complexity associated with the cancellations of subscriber ... more Absfruct -To reduce the echo canceler complexity associated with the cancellations of subscriber loop echo responses with long tails, we propose and investigate a hvo-stage digital echo canceler, in which the second stage is an adaptively weighted combination of orthonormal IIR responses. Satisfactory performance (70-dB cancellation) was found for a variety of loops at 80 and 320 kbaud symbol rates with 15 such IIR responses, based on Laguerre functions. The first echo canceler stage is a conventional transversal filter with 20-40 tap coefficients. Substantial complexity reduction was achieved by the new structure. Adaptation convergence was also analyzed and simulated.
Proceedings of 1997 Wireless Communications Conference, 1997
Abstract This paper reports on the work performed on the broadband indoor 29.5-GHz radio channel ... more Abstract This paper reports on the work performed on the broadband indoor 29.5-GHz radio channel measurements employing a directional-to-directional antenna configuration. The use of a programmable array antenna at the receiver allows investigations of the channel behavior for various reception angles. The reported results include the channel delay spread properties, the angle-dependent received power, and the correlation of two signals of different reception directions
Canadian Conference on Electrical and Computer Engineering 2004 (IEEE Cat. No.04CH37513), 2004
Augmentation of the conventional cellular networks with wireless fixed relays, to enable multi-ho... more Augmentation of the conventional cellular networks with wireless fixed relays, to enable multi-hop communications, is being considered for beyond-3G cellular networks in order to provide high data rate coverage in a cost-effective manner. In this paper, we consider a Cellular Relay Network (CRN) where a large number of low-complexity/low-power wireless fixed relays are deployed around the central node (equivalent of a BS) in each cell. Each relay and central node covers only a small area with a small amount of power, enabling the reuse of the frequency-time resources. The contribution of this paper is to evaluate the cell capacity (i.e., aggregate throughput) in the CRN which enables to make comparisons between the cell capacities of the CRN and the conventional cellular network. The paper shows that the cell capacity of the CRN does not depend on the cell size or the total number of relays in the cell, but it rather depends on the number of nearest relays to the central node.
In this paper, we consider the uplink of SC-based (single-carrier) block transmission systems whe... more In this paper, we consider the uplink of SC-based (single-carrier) block transmission systems where the transmission bandwidth associated to each channel, exceeds the symbol rate and we can have significant overlapping between adjacent channels. We present an iterative frequency-domain receiver for joint equalization and ACI (adjacent channel interference) suppression taking advantage of spectral correlations for the separation of cyclostationary signals.
A new PHASE algorithm is proposed for blind adaptive extraction of signal in the presence of inte... more A new PHASE algorithm is proposed for blind adaptive extraction of signal in the presence of interference by cyclostationary signal processing using an antenna array. The algorithm operates in an interference-limited system in which the desired and interfering signals have equal symbol rates, but slightly different carrier frequencies. Compared to the SCORE algorithm and a modified version of SCORE, the
The paper concerns the feasibility and achievable performance of adaptive filtering in an interfe... more The paper concerns the feasibility and achievable performance of adaptive filtering in an interference-limited multipath fading environment as encountered in indoor wireless communications. In a typical cellular radio application, the performance-limiting impairment is interference due to synchronous data streams from other co-channel and adjacent channel users (CCI and ACI). The receiver under consideration employs an adaptive fractionally spaced decision feedback
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Papers by David Falconer