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In this paper, an orthogonal space-time (ST) block coding technique for continuous phase modulation (CPM) is proposed and is combined with frequency-domain equalization (FDE) to obtain high diversity gains over the frequency-selective fading channels. The proposed technique maintains the constant envelope and the phase continuity of the CPM waveforms perfectly by using appropriate tail symbols during...
The use of multiple antennas for diversity and array gain may require accurate channel state information (CSI) on each subcarrier in orthogonal frequency division multiplexing systems. Such CSI is usually reported from the receiver to the transmitter, causing a significant amount of feedback signaling burden. Recent work can noticeably reduce the feedback signaling burden by exploiting the channel...
Error propagation of source-relay (S-R) link limits the performance of decode-and-forward (DF) relay system and prohibits cooperative DF relay system from achieving full diversity gain. In order to resolve these problems, we first derive the criterion to achieve full diversity. It explains why the SNR of S-R link would be better than other links. Using the criterion, the proposed strategy of positioning...
End-to-end delay is an important parameter in evaluating the performance of multihop ad hoc networks. To improve that, an efficient queue management scheme should be developed. Most existing queue management schemes do not take into account the number of hops that a packet traversed to reach its destination. In this paper, an efficient queue management scheme is proposed. The principal feature of...
Direct sequence ultra wide band (DS-UWB) is a wireless communication technique using codes to spread the transmitted data over a bandwidth in the order of 1.3 GHz. As the targeted data rate increases, shorter spreading codes are used, leading to a higher sensitivity to inter symbol interference (ISI). This paper presents a comparative study on the effect of different spreading codes on the system...
In this paper, we propose a computationally efficient precoding algorithm based on an iterative QRD-M for multiuser MIMO broadcast system. It has been shown that the iterative QRD-M algorithm can achieve near-ML performance with lower complexity at MIMO detection. Using depth first tree-search strategy, the first full expansion is tried by selecting the first level node with a minimum metric, constituting...
In this paper, multiple antenna based intercell interference mitigation techniques are studied in the downlink of an OFDM-based cellular radio network. At the base stations, multiple antennas are used for transmit beamforming in order to reduce the intercell interference spatially spread in the network. At the user terminals, multiple receive antennas facilitate implementation of interference rejecting...
Space-time block code from coordinate interleaved orthogonal design (STBC-CIOD) is considered as an effective transmit diversity scheme for achieving full-rate and full-diversity with low decoding complexity. The simple maximum likelihood (SML) decoder for STBC-CIOD is known to be an optimal decoder in time-invariant channel. However, the performance of the SML decoder is inevitably degraded when...
For evolution of the GSM/EDGE radio access network (RAN), the use of higher order modulation like 16- and 32-ary quadrature amplitude modulation (QAM) is considered in standardization for increased peak data rates and reduced transmission delays. In this paper, an optimized receiver design for different packet data transmission schemes is proposed. Turbo coding and turbo equalization is discussed...
In this paper we present the evaluation of a receiver signal processing chain for a 3GPP long term evolution (LTE) terminal, including coarse synchronisation, channel estimation, fine syncronisation (tracking), MIMO equalization and detection. Algorithm blocks are first individually explained and simulatively evaluated with a realistic channel model. Adjustments of the blocks to each other for improved...
A critical performance issue in providing VoIP service over wireless LANs is the voice packet delay due to handoffs as the user roams across different radio coverage regions. Most the recent research has focused on proactive approaches where control messages are transmitted from the mobile to prepare the access point and the other network nodes before the actual handoff occurs. Consequently, there...
The goal of this work is to analyse how UMTS behaves when HSDPA is implemented. A theoretical model was developed, calculating network capacity, for a sector of a cell, focusing on the analysis of parameters, such as the number of served users, throughput, and cell radius. Two scenarios were assessed with different userspsila distribution. Two analyses are done: one until the network saturates, and...
In the well-known distributed target-SIR tracking power control algorithm, when the target-SIR requirements are not reachable for all users (due to heavy load and/or deep fading), some users transmit at maximum power without reaching their target SIR. Such users inefficiently consume their energies, and introduce unnecessary interference to others, which in turn results in more unnecessary non-supported...
This document presents a new way to carry the Iub traffic in a 3G system through the use of the Uu radio RLC, MAC and WCDMA protocol layers. So, instead of using leased lines, Ethernet, microwave, this system uses its own 3G frequency to carry the traffic between different Nodes B. On top of that, it is possible to form a meshed network among the Nodes B maximizing the use of the lub interface and...
We present a realtime implementation of the time-critical core functions for 12 times 12 MIMO-OFDM (12 data streams) with LTE parameters on a cell broadband engine processor. An MMSE equalizer matrix update interval of 1 ms (high mobility) is achieved with less than 50% CPU utilization. Concurrent bidirectional processing (precoding and postprocessing) is shown to be feasible with this update rate.
A new MIMO detector for frequency selective indoor channels is proposed. The detector is based on a two-stage detection followed by a decision feedback equalizer (DFE). The first detection stage is assured by a linear equalizer subsequently followed by a decision unit. The second step is a reduced search (RS) around the solution acquired by the linear equalization, which will be performed in an efficient...
Multiple input multiple output (MIMO) detection methods are derived with an assumption that the noise power of all receiving paths are equal. This assumption is not valid in practical systems performing automatic gain control (AGC) which adjusts the signal level to the dynamic range of analog to digital converters (ADC). If the independent AGC scheme with the different gain for each receiving path...
In this paper, we make an attempt to integrate the features of scalable video coding (SVC) into current OFDM based mobile communications systems for improving the broadcast data rates and to provide a better coverage. Several physical- and MAC-layer concepts that quality for the use in combination with SVC are evaluated. Space time coding in combination with single carrier frequency division multiplexing...
This paper investigates the performance of the downlink in Multi Carrier CDMA (MC-CDMA) systems using a channel model from in-the-field propagation measurements. Results are presented also for channel models having non-exponentially decaying profiles. Channel coherence bandwidth (Bc) is incorporated within the analysis in order to demonstrate the effect of channel frequency selectivity on system performance...
In this paper, we propose a scalable speech/audio coder control algorithm to improve quality of service (QoS) of voice over IP (VoIP) calls over wireless local area networks (WLANs). There is an upper bound on the number of simultaneous VoIP calls that can be connected in a basic service set (BSS) of 802.11 WLANs which can be composed of an access point (AP) and wireless stations (WSTAs). In the case...
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