99,912 research outputs found
LAS-CDMA using Various Time Domain Chip-Waveforms
LAS CDMA exhibits a significantly better performance than that of classic random code based DS-CDMA, when operating in a quasi-synchronous scenario. Classic frequency-domain raised cosine Nyquist filtering is known to show the best possible performance, but its complexity may be excessive in highchip-rate systems. Hence in these systems often low-complexity time-domain waveform shaping is considered. Motivated by this fact, the achievable performance of LAS-CDMA is investigated in conjunction with three different time-limited chipwaveforms, which exhibit an infinite bandwidth. The raised cosine time-domain waveform based DS-CDMA system is shown to achieve the best performance in the context of a strictly band-limited system, because its frequency-domain spectral side-lobes are relatively low
On the Uplink Performance of Asynchronous LAS-CDMA
In this paper closed-form formulae are derived for characterizing the BER performance of Large Area Synchronous CDMA (LAS-CDMA) as a function of both the number of resolvable paths Lp and the maximum delay difference τmax, as well as the number of users K, when communicating over a Nakagami-m fading channel. Moreover, we comparatively studies the performance of LAS-CDMA and the traditional random code based DS-CDMA
Coding against Spreading Gain Optimization of Nonbinary BCH Coded CDMA System
The joint analytical optimisation of the spreading gain and coding gain of nonbinary BCH coded CDMA communication systems is considered in both single-cell and multi-cell scenarios. Furthermore, two types of detectors were employed, namely the minimum mean square error multiuser detector and the classic single-user matched filter detector. It is shown that the optimum coding rate varied over a wide range
Joint Pushing and Caching with a Finite Receiver Buffer: Optimal Policies and Throughput Analysis
Pushing and caching hold the promise of significantly increasing the
throughput of content-centric wireless networks. However, the throughput gain
of these techniques is limited by the buffer size of the receiver. To overcome
this, this paper presents a Joint Pushing and Caching (JPC) method that jointly
determines the contents to be pushed to, and to be removed from, the receiver
buffer in each timeslot. An offline and two online JPC policies are proposed
respectively based on noncausal, statistical, and causal content Request Delay
Information (RDI), which predicts a user's request time for certain content. It
is shown that the effective throughput of JPC is increased with the receiver
buffer size and the pushing channel capacity. Furthermore, the causal feedback
of user requests is found to greatly enhance the performance of online JPC
without inducing much signalling overhead in practice.Comment: 6 pages, 4 figure
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