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This paper addresses the problem of timing synchronization at the destination node of a non-regenerative wireless relay network which employs the IEEE 802.11a standard for data transmission. The two-hop relay network consists of an IEEE 802.11a-compliant source and destination pair, each equipped with a single antenna, aided by a relay node equipped with two antennas, which operate in half-duplex...
Relay transmission has been incorporated in the 3rd Generation Partnership Project (3GPP) for Long-Term Evolution (LTE) Enhancements (LTE-Advanced, or LTE-A). To effectively harvest the performance gain introduced by the relay transmission, wireless network coding techniques can be adopted. In this paper, using a simple three-node cooperative relay channel model, based on the decode-and-forward protocol,...
In this paper, a linearly coded (LC) relaying scheme is proposed for multiuser relay network in which a number of users communicate simultaneously with a common destination with the help of one relay node, by using orthogonal frequency division multiple access (OFDMA). The proposed linear coding at the relay node enables exploiting the frequency diversity in the relay-to-destination (R-to-D) link...
In this paper, we propose a double space-time transmit diversity (DSTTD)-based two-path relay system with power allocation and link combining methods. The two-path relaying protocol can restore spectral efficiency decreased due to the half-duplexing at the relay nodes and the DSTTD method can appropriately achieve the diversity gain from the two paths. To circumvent severe performance degradation...
Recently, there has been great interest in the multicast service where a common content such as video streaming and TV program is intended for multiple users. However, while receiving the common message, the users may also wish to receive their personal messages. Therefore, in this paper, we consider a multiple-antenna base station communicating with two single-antenna users and there are a common...
Opportunistic scheduling for wireless network coding (OWNC) combines the strategies of opportunistic scheduling and network coding. This paper applies two variants of OWNC on a two-user OFDMA system. Symbol-based OWNC decides a strategy from sum rate of the whole OFDM symbol. Subcarrier-based OWNC decides a strategy from the capacity on a subcarrier level. Novel algorithms are derived for power allocation...
Fountain codes are rateless erasure-correcting codes. Several fountain codes have been proposed recently to minimize overhead, many of which involve modifications of the Luby transform (LT) code. These fountain codes, like the LT code, have the implicit assumption that the probability distribution is fixed throughout the encoding process. In this paper, we will use the theory of posets to show that...
In this paper, we consider the half-duplex cooperative multiple-access channel (CMAC) in block-fading channels. Each link employs orthogonal frequency division multiplexing (OFDM) which is suitable for high rate wideband transmission and the modulated symbols are drawn from a finite constellation set. We first obtain the diversity order of the CMAC, as a function of the time sharing variables of the...
We derive in this paper the bit error probability and cutoff rate of an Amplify-and-Forward (AF) relay system operating in Rayleigh fast fading. In our model, we consider the relay thermal noise to be non-negligible and derive a closed form expression to approximate the bit error probability. Our approximated closed form expression matches well with simulation result. Using Chernoff bound, we upper...
A two-way relaying OFDM system based on the two-phase, amplify-and-forward protocol is considered. Preambles are designed for each of the sources with the criterion to minimize the Cramer-Rao bound (CRB) of the carrier frequency offset (CFO) estimate. The resulted CRB shows that it is possible for two-way relaying to incur only marginal loss from one-way relaying in CFO estimation under practical...
Coordinated multi-point transmission/reception (CoMP), in which base stations (BSs) cooperate during the downlink, has been identified as a tool for improving user rates and mitigating interference. The cost for existing coordination schemes with joint processing is the heavy exchange of channel state information and signal information over backhaul links. In this paper, we propose a decentralized...
Network MIMO, in which base stations cooperate and coordinate through a centralized design, is an attractive technology that promises higher spectral efficiency and lower inter-cell interference. However, such performance gain comes at the cost of extensive exchange of signal information (SI), channel state information (CSI), and coordinated precoding information over backhaul links. In this paper,...
In this paper, we consider the half-duplex relay channel. We seek to design multiple turbo codes to minimize the information outage in the block fading channel. An analysis on the diversity order of the relay channel, which depends on the time sharing variable and the rate of the code, is given for practical modulations. We also give a code structure for the multiple turbo codes to achieve the full...
In two-way relaying, two sources exchange information via a relay. In the generalized two-way relay, private information is also sent by each source to the relay, which may be used for overhead data, such as for channel state information. We consider the generalized two-way relay in a multi-carrier system over the wireless channel. Our problem is to maximize the rate that the sources exchange information,...
Cooperative system has been receiving considerable attention recently as an effective approach to improve transmission reliability in slow fading wireless channels. In this paper, we exploit cooperative diversity in multiple relay networks to improve the performance of Gaussian source transmission with layered broadcast coding. Specifically, we study the distortion performance of two amplify-and-forward...
Cognitive radio is widely expected to be the next Big Bang in wireless communications. Government spectrum regulatory committees in many countries have been taking steps to open the door to dynamic spectrum access using this technology and also laying down the rules for its implementation. International organizations have also been striving for standardizing this technology for various applications...
In this paper, we consider the half-duplex cooperative multiple-access channel (CMAC). We seek to design multiple turbo codes to minimize the information outage in the block fading channel. Since we consider an outage to occur even if the message of one of the sources fails to be decoded successfully, we employ a joint network-channel coding approach in our design. The codes are optimized using the...
Average and outage capacities for nonidentical two-user opportunistic scheduling for wireless network coding (OWNC) are derived in this paper. Nonidentical user case represents a more realistic scenario in which two users have different average signal-to-noise ratio (SNR). Our derived analytical results corroborate with the simulation results in the performance evaluation of OWNC. Insight on the performance...
In multi-cell OFDMA systems, inter-cell interference can severely degrade the system throughput, particularly for cell-edge users. To mitigate the inter-cell interference problem, interference coordination is a promising approach that effectively restricts and allocates certain resources among users in different cells to minimize the effect of inter-cell interference. However, most approaches are...
The problem of multi-user cooperation to achieve cooperative diversity for single-antenna terminals is considered. A cooperative strategy is proposed which divides multiple users into groups with each group having two users as partners. The two users alternately transmit their own information first, then simultaneously amplify and forward the partner's data in the same channel. Comparing to the conventional...
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