M. Reza Soleymani

Space-time-frequency COFDM with power allocation for broadband wireless communications

A scheme consisting of a combination of orthogonal transmit diversity (OTD) and OFDM with power allocation is presented. The proposed scheme is a new approach to space-time-frequency coded OFDM (COFDM) that combines OFDM with orthogonal transmit diversity, power control and turbo codes so that the diversity in frequency, time and space is exploited to provide high quality of transmission for wireless communications over frequency selective fading channels with enhanced performance in terms of spectral and power efficiency.

Raptor Coding for Non-Orthogonal Multiple Access Channels

In this paper, we propose a scheme for increasing the capacity of a communication channel by overloading a pre-existing channel with a controlled interfering channel using Raptor code. Combination of Raptor code and use of interference cancellation in the resulting Multiple Access Channel (MAC) results in almost perfect removal of the effect of the interfering channel. Thus, the primary channels performance remains intact. As in the other MAC detection scenarios, for optimal performances, a power difference between the main and interfering transmitters is required. In the case that these two powers are equal, we propose a hard decision stage prior to the decoding at the destination in order to eliminate erased symbols. The proposed technique can also be used for increasing the capacity of forward and/or return links of the DVB Return Channel via Satellite (DVB-RCS).

Rateless codes for cognitive radio in a virtual unlicensed spectrum

In this paper we investigate the use of rateless codes by secondary users equipped with cognitive radio in a virtual unlicensed spectrum. Assuming a Poisson model for the arrival of primary users, we analyze the goodput and the throughput of secondary users. Rateless codes are used for transmitting the secondary data through parallel subchannels available in a spectrum. They can compensate for the packet loss in secondary transmission due to appearance of primary users. We calculate the overall frame error probability at the secondary receiver and use it for calculating the throughput and goodput. Numerical results indicate that LT codes as a class of rateless codes provide reliable transmissions with high throughput and small redundancy. Except for very small Poisson arrival rates, the throughput is much higher than the case without erasure coding. Therefore, in real-time multimedia transmission that retransmitting lost information packets is not possible, the use of rateless codes is very beneficial.

Snapshot Capacity of Multi Hop Ad Hoc Networks

This paper studies the single power vector (snap-shot) capacity of the multi hop ad hoc networks. In a previous work, we introduced the concept of snapshot capacity region and studied it extensively for the case of single hop ad hoc networks. Here, we extend the snapshot capacity region idea to the more general and practical case of multi hop ad hoc networks with the partial successive interference cancellation technique. First, we prove the existence of a minimal power vector for each rate matrix and then we find the necessary and sufficient conditions of the rate matrices to be on the border of the snapshot capacity region. At the end, a novel iterative algorithm is proposed to produce the border of the snapshot capacity region. This algorithm can be used as an admission control algorithm to achieve the snapshot capacity region with some modifications.

A new space-frequency-time block coded OFDM scheme for broadband wireless communications

In this paper, a new scheme for space-frequency-time block coded OFDM system is presented. In the proposed scheme, we considered a combination of high order space-time code with OFDM utilizing joint diversity of space-frequency-time over frequency selective fading channels to provide high quality of transmission for broadband wireless communications. Numerical results are provided for evaluating the performance of several forms of the proposed system.

Destination cooperation in interference channels

Multiple Input Multiple Output (MIMO) techniques are used to exploit spatial diversity and to achieve high bit rates required for emerging multimedia applications. Cooperative communication can be used to achieve the diversity gains typical of MIMO without the need for multiple antennas on the consumer units. In this paper, we investigate the use of receiving node (destination) cooperation. We evaluate the performance of destination cooperation in an interference channel (DC-IC). We compare the performance of this system with the baseline 2-user orthogonal channel method. We demonstrate that the 2-user DC-IC outperforms the baseline technique by far. This is due to the cooperative communication. In the cooperative scheme, the receiver nodes in the first time slot, decode the received information from both sources while in the second time slot they cooperate. The scheme provides both diversity and coding gain. Using a typical scenario, we illustrate the efficiency of employing such technique with and without channel coding. However, the proposed technology can be applied to consumer mobile communication devices such as smart phones, tablets, etc...

Successively Structured Gaussian Two-terminal Source Coding

AbstractMultiterminal source coding refers to separate encoding and joint decoding of multiple correlated sources. Joint decoding requires all the messages to be decoded simultaneously which is exponentially more complex than a sequence of single-message decodings. Inspired by previous work on successive coding, we apply the successive Wyner-Ziv coding, which is inherently a low complexity approach of obtaining a prescribed distortion, to the two-terminal source coding scheme. First, we consider 1-helper problem where one source provides partial side information to the decoder to help the reconstruction of the main source. Our results show that the successive coding strategy is an optimal strategy in the sense of achieving the rate-distortion function. By developing connections between source encoding and data fusion steps, it is shown that the whole rate-distortion region for the 2-terminal source coding problem is achievable using the successive coding strategy. Comparing the performance of the sequential coding with the performance of the successive coding, we show that there is no sum-rate loss when the side information is not available at the encoder. This result is of special interest in some applications such as video coding where there are processing and storage constraints at the encoder. Finally, we provide an achievable rate-distortion region for the m-terminal source coding.

Sending Correlated Gaussian Sources over a Gaussian MAC: To Code, or not to Code

We consider 1-helper problem in which one source provides partial side information to the fusion center (FC) to help reconstruction of the main source signal. Both sources communicate information about their observations to the FC through an additive white Gaussian multiple access channel (MAC) without cooperating with each other. Two types of MAC are considered: orthogonal MAC and interfering (non-orthogonal) MAC. We characterize the tradeoff between the transmission cost, i.e., power, and the estimation distortion, D, using Shannons separation source and channel coding theorem. We demonstrate that the separation-based coding strategy outperforms the uncoded transmission under an orthogonal MAC. However, in the symmetric case under an interfering MAC, below a certain signal- to-noise ratio (SNR) threshold, uncoded transmission outperforms the separation-based scheme. The threshold can be determined in terms of the correlation coefficient between the sources, p, and in fact is an increasing function of p. Finally, the optimal power scheduling to minimize the total power consumption in the network is derived.

An Energy-Efficient Cooperative Algorithm for Data Estimation in Wireless Sensor Networks

In wireless sensor networks (WSN), nodes operate on batteries and networks lifetime depends on energy consumption of the nodes. Consider the class of sensor networks where all nodes sense a single phenomenon at different locations and send messages to a fusion center (FC) in order to estimate the actual information. In classical systems all data processing tasks are done in the FC and there is no processing or compression before transmission. In the proposed algorithm, network is divided into clusters and data processing is done in two parts. The first part is performed in each cluster at the sensor nodes after local data sharing and the second part will be done at the fusion center after receiving all messages from clusters. Local data sharing results in more efficient data transmission in terms of number of bits. We also take advantage of having the same copy of data at all nodes of each cluster and suggest a virtual multiple-input multiple-output (V-MIMO) architecture for data transmission from clusters to the FC. A Virtual-MIMO network is a set of distributed nodes each having one antenna. By sharing their data among themselves, these nodes turn into a classical MIMO system. In the previously proposed cooperative/virtual MIMO architectures there has not been any data processing or compression in the conference phase. We modify the existing V-MIMO algorithms to suit the specific class of sensor networks that is of our concern. We use orthogonal space-time block codes (STBC) for MIMO part and by simulation show that this algorithm saves considerable energy compared to classical systems.

A novel coding strategy for device-to-device communications

Device-to-device communication is currently an active research topic in the cellular industry. D2D communication enables two mobile users in vicinity to directly communicate over a dynamically assigned, licensed spectrum without going through the base station. D2D offers tremendous benefits such as increase in spectral and energy efficiency, offload traffic of the base station and reduce transmission delay. In this paper, we first present an overview of 3GPP proximity services. Then, we propose a new coding strategy that considerably increases the efficiency of the channel in the multicast setting. Specifically, we study the scenario where three mobile devices are nearby and want to exchange their messages via a relay. Performance evaluation of the proposed scheme using Raptor codes shows that this scheme approaches the theoretical limits at moderate to high signal-to-noise ratio.