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This paper analyzes the performance of space-time block coded orthogonal frequency division multiplexing (OFDM) systems. In our analysis, we abandon the usually made assumption of quasi-static channel conditions. Instead of this, we consider the more general and realistic case that the channel envelope changes during two consecutive transmission time slots. In addition, we take the spatial correlation...
Video surveillance on public transport is a useful tool to fight against anti-social behaviour like vandalism, harassment, graffiti and terrorism. Real-time video surveillance on moving public transport faces serious technological challenges mainly due to limited throughput offered by existing communication technologies at high vehicular speeds. Success of real-time video surveillance on public transport...
On-body communication channels are of increasing interest as more and more wireless devices are wearable in medical, military and personal communication applications. Based on the previous study at 4.5GHz, this paper investigates reasons for time-varying fading of dynamic on-body channels. Antenna movements during action are categorized into intentional movement which can be controlled and unintentional...
In this paper, we analyze the impact of imperfect channel estimation on the performance of pilot symbol assisted modulation (PSAM) used in a relay communication system with distributed space time block code (STBC) and amplify-and-forward protocol. We derive correlation coefficients between the channel coefficients and their estimates when the relay-to-destination link is either non-fading or fading,...
An important transmitter adaptation technique used in multiple-input multiple-output (MIMO) communication systems is precoding based on the dominant right-singular vectors of the channel matrix. These vectors are typically estimated at the receiver, quantized, and fed-back to the transmitter via a low-rate feedback channel. We present a method for designing an efficient low-rate quantizer for the...
In this paper, we study the problem of joint carrier frequency offset (CFO) and channel estimation for two-way relay network (TWRN). We consider the frequency selective fading channels and adopt the zero padding (ZP) based orthogonal frequency division multiplexing (OFDM) as the modulation of the transmission. Due to the mixture of the first and the second transmission phases, the joint estimation...
We consider information reconciliation in secret key agreement from a fading channel where two legitimate parties utilize channel estimates of their fading channel as correlated random variables to generate a secret key. The information reconciliation is a process of correcting the discrepancies between the legitimate parties' keys by public discussion in the presence of eavesdropper, where the amount...
In selective cooperative relaying only a single relay out of the set of available relays is activated at a time, hence the available power and bandwidth resources are efficiently utilized. However, implementing selective cooperative relaying in time-varying channels may cause frequent relay switchings that deteriorate the overall performance. In this paper, we study the rate at which a relay switching...
In this paper, a low-complexity iterative receiver combining joint iterative channel estimation with symbol detection is proposed for coded orthogonal frequency division multiplexing (OFDM) systems in fast fading channels with Doppler frequencies up to 15% of the OFDM symbol rate. The receiver exchanges information between the channel estimator and detector in an iterative fashion to obtain accurate...
In mobile multimedia networks, different traffic classes require various levels of quality of service (QoS). In this paper, we propose a cross-layer design to provide diverse QoS provisions for integrated realtime/non-realtime traffic by jointly taking into account the physical layer, data link layer, and application layer. Specifically, at the physical layer, adaptive modulation and coding (AMC)...
This paper is concerned with a spectrum sharing cognitive radio network. In particular, the individual outage capacity region for a M-user fading cognitive multiple access network sharing the same spectrum with an existing primary network is first characterized. The primary network's transmission is assumed to be protected by the interference power constraint. Then, under the interference power constraint...
In this paper, a game-theoretic analysis for the resource allocation policies in fading multiple-access channels (MAC) in the presence of quality of service (QoS) constraints is performed. Effective capacity, which provides the maximum constant arrival rate, or throughput, that a given service process can support while satisfying statistical delay constraints, is considered in a multiuser scenario...
It is well known that symbol timing offsets larger than the cyclic prefix as well as carrier frequency offsets between transmitter and receiver stations destroy the orthogonality among OFDM subcarriers and induce additional interference. In conjunction with MIMO transmission on frequency selective fading channels where different users interfere with each other, these effects strongly degrades the...
Maximum Likelihood Detection (MLD) featuring Log-likelihood (LLR) combining technique has been introduced in earlier works to achieve diversity gains in block fading channels for one relay node. In this paper, we extend this strategy to multiple relay systems (MRS) and introduce a new method such that the computational complexity of MLD is further reduced. This method approximates bit LLR values from...
In this paper, cognitive transmission under quality of service (QoS) constraints is studied. In the cognitive radio channel model, it is assumed that both the secondary receiver and the secondary transmitter know the channel fading coefficients perfectly and optimize the power adaptation policy under given constraints, depending on the channel activity of the primary users, which is determined by...
This paper addresses the clustering problem for highly mobile ad hoc networks. In the proposed scheme, Doppler shifts associated with received signal are used to estimate the relative speed between cluster head and cluster members. With the estimated speed, a node can predict its stay time in every nearby cluster. In the initial clustering stage, a node joins a cluster that can provide it with the...
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