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Currently a number of 802.11 based standards support multiple rates at physical layer and recently 802.11 MAC protocols have been modified to make use of these multiple rates. Two such mechanisms, opportunistic auto rate (OAR) and receiver based auto rate (RBAR) have shown to improve throughput performance of wireless LANs as well as infrastructure-less wireless networks. However these protocols are...
We present an effective method of collision recovery for orthogonal frequency division multiplexing (OFDM)-based communications. For the OFDM system, the modulated message data can be demodulated using the partial time-domain OFDM symbol. Therefore, the partial time-domain symbol can be adopted to reconstruct the whole OFDM time-domain symbol with estimated channel information. This property can be...
We consider SINR maximizing receivers based on the concept of chip-level filtering and symbol level equalization for WCDMA downlink. In this contribution we propose a new class of receivers based on channel sparsifying linear pre-processing at chip-rate followed by time-varying symbol level equalizers. Due to a sparse structure imposed on the channel (i.e. sparsification) by a chip level pre-equalizer...
A distributed power, channel, and route selection scheme for multi-hop radio networks is proposed by extending multichannel asynchronous distributed pricing (MADP) algorithm, which is a power and channel selection scheme for single-hop radio networks. MADP algorithm achieves suboptimal system throughput in single-hop radio networks, however, since MADP algorithm allocates more resources to links with...
In this paper, a distributed power-aware medium access control (MAC) algorithm for ad hoc wireless networks is presented. The algorithm is developed based on proposing a power-aware MAC game which is analyzed in the game theory framework. The aim is to adjust each active link persistence probability and power by maximizing a defined local link payoff function. The payoff function is such that its...
Wireless channel qualities vary and degrade due to fading and interference. Cooperative communication has characteristics of spatial diversity and virtual antenna, and thus it can improve communication efficiency significantly. One of the essential design issues in cooperative communication is partner selection mechanism. In this paper, we propose a partner selection algorithm which utilizes two decision...
Increasing demand for high-speed and efficient multimedia transmission over wireless networks has driven tremendous research on enhancing the performance of multimedia communications over noisy channels. Multimedia applications increasingly require efficient transmission of still and moving images over wireless channels. In response to the rapidly increasing demand of the data-rate requirements, of...
In this paper we consider channel coding for dual data streams with unequal error protection (UEP) for the objectives of low complexity receiver structures and prioritized handling of data in MIMO broadcast systems. We focus on high spectral efficiency bit interleaved coded modulation (BICM) MIMO OFDM system where two independently coded spatial streams of symbols are simultaneously transmitted by...
We study the secrecy capacity of the frequency-selective wiretap channel. Assuming that a guard interval of L symbols is inserted to avoid the inter-block interference and these symbols are discarded at the receiver, the single-carrier frequency-selective channel is modeled as a multiple-input multiple-output Toeplitz matrix. For this special case of the MIMO wiretap channel and under the assumption...
The assignment of resources to the cells of a cellular mobile radio network is usually done by assigning certain parts of the total bandwidth to the cells. With the use of adaptive transmission, power can be considered as a resource and taking power into account in the assignment of resources to cells offers additional flexibility, especially in achieving efficient assignments and in adapting the...
This paper is focused on the design and analysis of power control procedures for the uplink of multipath code-division-multiple-access (CDMA) channels based on the large system analysis (LSA). Using the tools of LSA, a new decentralized power control algorithm aimed at energy efficiency maximization and requiring very little prior information on the interference background is proposed; moreover, it...
In this paper, we propose a new multiple-input-multiple-output (MIMO) transceiver for transmitted-reference impulse-radio ultra-wideband (TR-IR-UWB) communications. The proposed scheme is capable of achieving full spatial and multi-path diversity orders while assuring a simple symbol-by-symbol decodability with analog autocorrelation receivers that do not require any kind of channel estimation. This...
Two semi-blind tensor based receivers for uplink radio over fiber (ROF) nonlinear instantaneous channels in a multiuser code division multiple access (CDMA) environment are proposed in this paper. These receivers are based on the PARAFAC decomposition of a tensor (three-way array) composed of received signals with space, time and code diversities. A great advantage of the tensor approach is that it...
The capacity of a discrete-time memoryless Gaussian channel, where the channel state information (CSI) is neither available at the transmitter nor at the receiver, is addressed. A closed form expression of the optimal capacity-achieving input distribution at low signal-to-noise ratio (SNR) is derived, and the exact capacity of a non-coherent Single Input Single Output (SISO) channel is given. The...
This paper analyses busy burst (BB) enabled interference avoidance for multi-user orthogonal frequency division multiple access (OFDMA) in a Manhattan grid deployment scenario. Upon successful reception of data, the receiver transmits a BB in a time-multiplexed mini-slot. Exploiting the channel reciprocity of time division duplex (TDD), an exclusion region around a victim receiver is established,...
Radio networks experience the greatest spectrum scarcity in urban environments. Dynamic radio access enables simultaneous and opportunistic spectrum reuse. This paper considers frequency division duplexing cellular networks, where every mobile user (MU) is allocated a frequency channel for uplink transmission to the base station (BS). Previously a frequency reuse model has been proposed for low power...
We consider a cognitive radio scenario in which two (or more) operators providing services in the same area wish to share the same licensed band of spectrum. This scenario differs from the classical cognitive setup with a primary and a secondary operators, as both operators here are instead on an equal footing. The operators face the choice of competition or cooperation in the way they choose their...
Single frequency networks (SFN) in combination with a multi-carrier transmission scheme such as OFDM are often proposed as a means to provide continuous coverage of broadcast applications over a large area. While this combination does succeed in providing continuous coverage, it has certain limitations. Specifically, at points where signals from multiple base-stations are received, the overall signal-to-noise...
This paper presents a method to counteract the detrimental effects of carrier frequency offsets (CFOs) in the uplink of OFDMA-based wireless networks. The CFO values of different users are first estimated from the received decomposed signal using the best linear unbiased estimator (BLUE). The CFOs effects are then compensated based on the estimated values and also taking advantage of an iterative...
The accurate determination of the link quality is critical for ensuring that functionalities such as intelligent routing, load-balancing, power control and frequency selection operate efficiently. There are 4 primary metrics for capturing the quality of a wireless link: RSSI (Received Signal Strength Indication), SINR (Signal-to-Interference-plus-Noise Ratio), PDR (Packet-Delivery Ratio), and BER...
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