Showing papers in "European Transactions on Telecommunications in 2005"
TL;DR: Different cooperative relaying protocols are studied and their performance with that of direct transmission and conventional relaying is compared to confirm that cooperative relays is an effective means of enhancing the performance of wireless systems whenever temporal and frequency diversity is scarce.
Abstract: Cooperative relaying recently emerged as a viable option for future wireless networks. By simultaneously exploiting path loss savings known from relaying scenarios and the diversity inherent to any scheme involving spatially separated transmitters, this technique is able to leverage gains from both relaying and spatial diversity techniques. In this paper, we study different cooperative relaying protocols and compare their performance with that of direct transmission and conventional relaying. We investigate under which conditions the developed techniques provide gains over other approaches. Our results confirm that cooperative relaying is an effective means of enhancing the performance of wireless systems whenever temporal and frequency diversity is scarce.
162 citations
TL;DR: A model has been built based on data from a real network and the automated diagnosis system has been used to classify problems in a cellular network, showing that the solution is easily implemented and that the diagnosis accuracy is very high, therefore leading to a reduction in the operational costs of running the network.
Abstract: This paper presents a system for automated diagnosis of problems in a cellular network, which comprises a method and a model. The reasoning method, based on a naive Bayesian classifier, can be applied to the identification of the fault cause in GSM/GPRS, 3G or multi-systems networks. A diagnosis model for GSM/GPRS radio access networks is also described, whose elements are available in the network management systems (NMSs) of most networks. It is shown that the statistical relations among the elements, that is the quantitative part of the model, under certain assumptions, can be completely specified by means of the parameters of beta density functions. In order to support the theoretical concepts, a model has been built based on data from a real network and the automated diagnosis system has been used to classify problems in a cellular network, showing that the solution is easily implemented and that the diagnosis accuracy is very high, therefore leading to a reduction in the operational costs of running the network. Copyright © 2005 AEIT.
70 citations
TL;DR: It turns out that the ergodic capacity in all cases can be expressed in terms of a sum of determinants with elements that are a combination of polynomials, exponentials and the exponential integral E 1 solely.
Abstract: We present a novel mathematical approach that for the first time allows for calculating the moment generating function (MGF) of mutual information of Rayleigh fading MIMO channels with arbitrary fading correlation at transmitter and receiver. Specifically, we make use of certain hypergeometric functions of matrix argument, which are frequently used in multivariate statistics. This allows for a concise general expression for the MGF and we specialise the general result to scenarios with one-side correlated and uncorrelated channels. Using the MGF, we derive exact formulas of the ergodic capacity, thus unifying the capacity analysis of correlated Rayleigh fading MIMO channels. It turns out that the ergodic capacity in all cases can be expressed in terms of a sum of determinants with elements that are a combination of polynomials, exponentials and the exponential integral E 1 solely. The analysis is verified by Monte-Carlo simulations and shows a perfect match.
68 citations
TL;DR: This paper presents a model of wireless networks providing voice and data services at hot spots in terms of a BMAP/ PH/N retrial queue in order to provide evidence that 'correlation matters'.
Abstract: In teletraffic engineering, the effective design of wireless networks providing voice and data services at hot spots is of great practical importance. This paper presents a model of such networks in terms of a BMAP/ PH/N retrial queue. Due to the batch occurrence and high correlation of the traffic, it is decisive to choose the correct Batch Markovian Arrival (BMAP) representation of the empirically observed streams of call requests. The numerical results show that there are great differences in important performance measures due to different structures of the chosen BMAP which have the same fundamental rate and the same coefficient of variation of the inter-arrival times. The paper again provides evidence that 'correlation matters'. Yet, further examples show that the coefficient of correlation is not the single characteristic (besides the fundamental rate and coefficient of variation) of the arrival process that has an influence on the performance of the network.
27 citations
TL;DR: In this article, the authors compare the performance of some opportunistic scheduling schemes using a flow-level approach where the random evolution of the number of ongoing flows is explicitly taken into account.
Abstract: While fading effects have long been combatted in 2G wireless networks, primarily devoted to voice calls, they are now seen as an opportunity to increase the capacity of 3G networks that incorporate data traffic. The packet delay tolerance of data applications, such as file transfers and Web browsing for instance, allows the system flexibility in scheduling a user's packets. So-called opportunistic scheduling, which ensures transmission occurs when radio conditions are most favourable, is the key component of currently developed systems like cdma2000 IS-856 and UMTS HSDPA. We compare the performance of some scheduling schemes using a flow-level approach where the random evolution of the number of ongoing flows is explicitly taken into account.
25 citations
TL;DR: An iterative algorithm of polynomial complexity is presented that solves a max-min fairness problem which is often encountered while dealing with traffic routing or capacity allocation problems.
Abstract: An iterative algorithm of polynomial complexity is presented that solves a max-min fairness problem which is often encountered while dealing with traffic routing or capacity allocation problems. The algorithm does not depend on any specific traffic routing problem formulation and is sufficiently general to be applied to a broad class of traffic routing and capacity allocation problems. The correctness of the algorithm and its complexity are formally proved.
25 citations
TL;DR: In this paper, the authors provide a first step to the robustness analysis of a reputation system based on the deviation test as introduced in [6], and show that the system exhibits a phase transition: in the subcritical regime, the reputation system is robust and the lying has no effect.
Abstract: Self-organized networks require some mechanism to ensure cooperation and fairness in the face of individual utility maximizing users and potential malicious attacks. Otherwise, network performance can be seriously deteriorated. One promising approach are decentralized reputation systems. However, these are vulnerable to users with an interest in passing on false information. Robustness against liars has not yet been analyzed in detail. In this paper, we provide a first step to the robustness analysis of a reputation system based on the deviation test as introduced in [6]. Users accept second hand information only if this does not differ too much from their reputation values. We show that the system exhibits a phase transition: In the subcritical regime, the reputation system is robust and the lying has no effect. In the supercritical regime, the lying does have an impact. We obtain the exact critical values via a mean field approach. We then use explicit computation to verify the mean field results. Thus, we can give conditions under which the deviation test makes the reputation system robust. We also obtain quantitative results on what goes wrong in the supercritical regime.
23 citations
TL;DR: This work analyses the performance of RSA- and ECDSA-based digital signature schemes in the context of multi-hop ad hoc networks and draws some recommendations to strengthen the security engineering process for dependable distributed systems over the wireless network.
Abstract: Cryptographic primitives need to be carefully evaluated when being applied in components ensuring enhanced protection aims. This work analyses the performance of RSA- and ECDSA-based digital signature schemes in the context of multi-hop ad hoc networks. Our work shows that contrary to a single wireless hop scenario with restricted clients in the wireless network and a powerful server in the fixed network, the choice of an appropriate signature candidate is not as obvious as for the aforementioned architecture. Our performance analysis considers three partially interdependent axes (a) the required security level, (b) the device restriction and (c) the protocol specification with the required security relationships, and the assumed traffic flow. We take (c) into account by analysing two charging protocols for wireless multi-hop scenarios. By generalising our observations, we carefully derive some recommendations to strengthen the security engineering process for dependable distributed systems over the wireless network. Copyright © 2005 AEIT.
23 citations
TL;DR: Both quantitative measurements and results of quality perceived by users of IPv6 multimedia applications are provided, showing that Fast Handovers for MIPv6 approach is good enough even for multimedia applications with strict real-time requirements.
Abstract: The EU IST project Moby Dick worked with the vision, shared by many other researchers, that Next Generation Networks will be based on IPv6 with mobility, security and quality of service (QoS) support. These networks will offer all kinds of services, including multimedia ones with real-time requirements, traditionally offered by circuit switched technologies. The IETF has finished the standardization of a solution for mobility in IPv6 networks: Mobile IPv6 (MIPv6). Additional protocols are being discussed to improve the performance of Mobile IPv6 to support real-time traffic during handovers; one of these proposals is Fast Handovers for MIPv6. This paper analyzes experimentally—using real implementations for Linux O.S.—the performance of MIPv6 and Fast Handovers for MIPv6, to study if the performance is acceptable for multimedia applications. Both quantitative measurements and results of quality perceived by users of IPv6 multimedia applications are provided, showing that Fast Handovers for MIPv6 approach is good enough even for multimedia applications with strict real-time requirements. Copyright © 2004 AEI.
19 citations
TL;DR: A finite-source feedback queueing model for this access mode of the IEEE 802.11 medium access control protocol based on the mechanism of carrier sense multiple access with binary exponential backoff is developed.
Abstract: The most mature medium access control protocol for wireless local area networks is the IEEE 802.11 standard. The primary access mode of this protocol is based on the mechanism of carrier sense multiple access with binary exponential backoff. We develop a finite-source feedback queueing model for this access mode. In this model, we derive expressions for the throughput and the first moment of the delay and a set of equations to compute the Laplace Stieltjes Transform and higher moments of the delay. The accuracy of the model is verified by simulation.
18 citations
TL;DR: The saddle-point method of integration is used to derive a non-recursive approximation for the distribution of occupied bandwidth units of the multirate loss system with complete sharing, which achieves complexity O(1) per state.
Abstract: The saddle-point method of integration is used to derive a non-recursive approximation for the distribution of occupied bandwidth units of the multirate loss system with complete sharing, which achieves complexity O(1) per state. For the multirate finite sources model an asymptotic scaling is assumed in which the capacity and the number of sources are large and as an application the tail probability is approximated in the region 10 -4 -10 -10 . The limits for the infinite sources model are obtained as well and the approximate distribution is used to initialise a partial recursion, which transforms the state probabilities into an approximate distribution of the same system with trunk reservation. As a result the blockings are obtained with a low numerical complexity, which scales independent of the capacity. Numerical results show the accuracy and efficiency of the approximations. The estimate of the tail probability is shown to be superior if compared to the modified Chemoff bound.
TL;DR: It is argued that access to wireless LAN hotspots can be shared in a peer-to-peer manner and enables unified wireless LAN roaming without central authorities and without the administrative overhead that is usually associated with such efforts.
Abstract: We argue that access to wireless LAN (WLAN) hotspots can be shared in a peer-to-peer manner. In the hotspot-sharing scheme that we propose, peers are encouraged to keep their residential WLANs open, offering Internet access to peers passing by. We call our scheme peer-to-peer wireless network confederation (P2PWNC). Payments in P2PWNC are only ‘in kind’. We are motivated by the widespread availability of wireless LAN equipments and the proliferation of residential broadband connections. P2PWNC enables unified wireless LAN roaming without central authorities and without the administrative overhead that is usually associated with such efforts. In this paper, we present and evaluate the decentralised design of P2PWNC. Copyright © 2005 AEIT.
TL;DR: This paper presents the admission control (AC) algorithms that are implemented in the prototype multi-service AQUILA QoS IP network, developed for regulating traffic submitted to network services dedicated for handling real-time streaming traffic of variable bit rate type and elastic traffic, produced by greedy TCP sources.
Abstract: This paper presents the admission control (AC) algorithms that are implemented in the prototype multi-service AQUILA QoS IP network [4]. The discussed algorithms were developed for regulating traffic submitted to network services (NS) dedicated for handling: (1) real-time streaming traffic of variable bit rate (VBR) type and (2) elastic traffic, produced by greedy TCP sources. For the former NS, named Premium VBR, the measurement-based AC (MBAC) scheme is proposed. The applied approach employs the well-known Hoeffding bound formula [2] for calculating required link capacity to assure packet loss ratio at a predefined level. Moreover, this method is supported by the declarations about the peak bit rate as well as by the measurements of mean bit rate on aggregate flow level. For the latter NS, named premium multimedia, two alternative AC algorithms are investigated, both designed for assuring requested TCP throughput. While the first of them follows the token bucket marking (TBM) concept [12], the second one adjusts the advertised TCP window size to enable an ideal TCP behaviour (i.e. lossless packet transfer). The simulation results are included for illustrating the advantages of the discussed algorithms.
TL;DR: To evaluate the distribution function of a sum of lognormal random variables, it is common to use approximation methods based on moment matching, which include the classical and simple Fenton-Wilk methods.
Abstract: To evaluate the distribution function of a sum of lognormal random variables. it is common to use approximation methods based on moment matching. These include the classical and simple Fenton-Wilk ...
TL;DR: In this article, a closed-form expression for the average output signal-to-noise ratio (SNR) of an L-branch receiver employing equal-gain combining (EGC) was derived.
Abstract: In this letter, capitalising on a recently presented expression for the joint probability density function of the Weibull fading statistical model, a novel closed-form expression is derived for the average output signal-to-noise ratio (SNR) of an L-branch receiver employing equal-gain combining (EGC). The obtained expression includes the case of correlative fading with arbitrary correlation among the input branches, as well as non-identical fading statistics. Numerical results depict the effects of the fading severity, the fading correlation and the number of diversity branches, on EGC performance. An interesting outcome is that the average output SNR is not a clear and meaningful measure for the EGC receivers performance, when these operate in correlative fading channels. Copyright © 2005 AEIT.
TL;DR: A novel swarm intelligence inspired routing algorithm, emergent ad hoc routing algorithm (EARA), for mobile ad hoc networks, based on the understanding of the evolutionary cooperation in the biological swarm, which provides an alternative solution resilient against changes in the dynamic environment.
Abstract: This paper presents a novel swarm intelligence inspired routing algorithm, emergent ad hoc routing algorithm (EARA), for mobile ad hoc networks. Based on the understanding of the evolutionary cooperation in the biological swarm, which provides an alternative solution resilient against changes in the dynamic environment, we use the principle of swarm intelligence for the reinforcement of optimal routes with only local communication (here, local communication is defined as the neighbour-to-neighbour Communication). The data traffic is influenced at each node, and the communicating nodes observe this influence to update their tables. The concept of stigmergy is adopted to reduce the amount of control traffic to improve the performance of the system. We also include an evaluation methodology to simulate ad hoc networks, and the simulation results show that this routing algorithm scales well to a variety of network conditions. Copyright © 2005 AEIT.
TL;DR: This paper considers iterative receiver techniques for the downlink in WCDMA systems (UMTS FDD mode) by applying polynomial expansion to the LMMSE receiver, and obtains an iterative solution in which the complexity per iteration becomes comparable to twice that of the Rake receiver.
Abstract: In this paper, we consider iterative receiver techniques for the downlink in WCDMA systems (UMTS FDD mode). We start from the linear minimum mean square error (MMSE) receiver (at symbol level), which is time varying and hence too complex to implement. By applying polynomial expansion (PE) to the LMMSE receiver, an iterative solution is obtained in which the complexity per iteration becomes comparable to twice that of the Rake receiver. Our one contribution is to replace the channel matched filter by a channel equaliser within this PE to accelerate the convergence of the iterations. We also investigate various scenarios for the introduction of non-linearities in the PE scheme that are particularly applicable to the multicode case of the high speed downlink packet access (HSDPA) mode since it is well known that non-linearities in the PE scheme lead, in fact, to the parallel interference canceler (PIC).
TL;DR: A specific MAC structure is selected enabling the operation of a dynamic OFDM system, incorporating a signalling scheme for dynamically assigned sub-carriers, and it is found that a realistic overhead model decreases the performance of both static and dynamic schemes.
Abstract: Dynamically assigning sub-carriers of orthogonal frequency division multiplexing (OFDM) systems to multiple different terminals in a cell has been shown to be beneficial in terms of different transmission metrics. The success of such a scheme, however depends on the ability of the access point to inform terminals of their newest sub-carrier assignments as well as on the accuracy of the channel state information used to generate new assignments. It is not clear whether the overhead required to implement these two functions consumes all of the potential performance increase possible by dynamically assigning sub-carriers. In this paper, a specific MAC structure is selected enabling the operation of a dynamic OFDM system, incorporating a signalling scheme for dynamically assigned sub-carriers. Based on this structure, we study the overhead required for a dynamic sub-carrier scheme; a static variant that serves as a comparison case. We investigate the performance difference of these two schemes for various scenarios where at first signalling and then realistic channel knowledge is added to the system model. Average throughput and goodput per terminal serve as figures of merit; the number of terminals in the cell, the transmission power per sub-carrier, the delay spread and the movement speed of the terminals are varied. We find that a realistic overhead model decreases the performance of both static and dynamic schemes such that the overall ratio favours in all cases except for higher speeds the dynamic rather than the static scheme especially in realistic system environments.
TL;DR: For non-data-aided carrier phase recovery of M-ary phase-shift keying (MPSK) as modulation scheme, Viterbi andViterbi (V&V) suggested a feedforward (FF) variant of the Mth-power non-linearity, and a closed-form solution has been presented for even integer values of the generic design parameter m.
Abstract: For non-data-aided carrier phase recovery of M-ary phase-shift keying (MPSK) as modulation scheme, Viterbi and Viterbi (V&V) suggested a feedforward (FF) variant of the Mth-power non-linearity. With respect to the jitter variance, a closed-form solution has been presented for even integer values of the generic design parameter m, 0 ≤ m ≤ M. Basically, the V & V principle may be applied to feedback (FB) systems as well, where little is found in the open literature. To this end, the characteristic of the open loop (S-curve) is derived in closed form for any value of m. The jitter variance of the linearized FB synchronizer is then computed using the slope in the stable equilibrium point of the S-curve. Furthermore, in order to minimize the jitter variance, it is shown that the optimized value mopt 1 for increasing values of the signal-to-noise ratio (SNR), whereas in the opposite case mopt M. Finally, it is verified that the developed relationships are also valid for FF estimators if they are operated with negligible carrier frequency offsets. Copyright © 2004 AEI.
TL;DR: This paper shall explain and show that these two architectures can be systematically related and viewed as a unified concept and a new way of looking at the fully survivable network design helps to understand clearly the mechanisms and performance of each protection strategy.
Abstract: This paper presents a comprehensive investigation of a wide range of protection strategies against all single link failures in all-optical wavelength division multiplexing (WDM) networks based on mesh and multi-ring architectures. In the mesh architecture, three protection strategies namely, minimal cost, single link basis and disjoint path protection strategies are investigated. In the multi-ring architecture, the distribution and non-distribution traffic multi-ring design strategies are extensively examined. Although, the concepts of mesh and multi-ring designs have previously been perceived to be fundamentally different, in this paper, we shall explain and show that these two architectures can be systematically related and viewed as a unified concept. This new way of looking at the fully survivable network design helps us to understand clearly the mechanisms and performance of each protection strategy. In addition, this approach allows us to see the trend of fiber-cost requirements that increase step-by-step from the most complicated mesh protection to the simplest multi-ring protection architectures. To minimize the system cost of 100% protection WDM networks, mathematical models based on the integer linear programming (ILP) are derived as the tool for achieving optimal path placement, wavelength assignment and ring selection simultaneously. Apart from the mathematical model, the main contributions of this paper are the analysis and comparison in aspects of the spare capacity requirement and ease of operation and practical feasibility amongst these protection strategies. However, the emphasis will be on the multi-ring protection schemes. In addition, the influence of the number of multiplexed wavelengths per fiber to design outcomes and the benefit of having wavelength conversion capability in WDM network environment are also studied. Copyright © 2004 AEI.
TL;DR: This letter proposed a blind channel identification and equalisation algorithm, based on the eigenanalysis of shifted correlation matrices of the received data and their associated properties, which is robust to channel order overestimation and not sensitive to noise as well.
Abstract: Subspace (SS) methods are effective approaches for blind channel identification, for they achieve a good performance with a relatively short data lengths and work well at low signal-to-noise ratio (SNR). However, they require accurate channel order estimation, which is difficult in a noisy environment. Although linear prediction (LP) methods can handle the problem of channel order overestimation, their performance degrades dramatically when SNR is low. In this letter, we proposed a blind channel identification and equalisation algorithm, based on the eigenanalysis of shifted correlation matrices of the received data and their associated properties. The algorithm is robust to channel order overestimation and not sensitive to noise as well. Furthermore, the algorithm does not require the computation of the correlation matrix pseudo-inverse, as with linear prediction algorithms, nor are the whole noise or signal eigen vectors necessary to achieve identification as with the subspace algorithm, so it is computationally efficient. Copyright © 2005 AEIT.
TL;DR: An optimal solution of the call admission control and routing problem in multi-service loss networks, in terms of average reward per time unit, is possible by modeling the network behavior as a Mar network.
Abstract: An optimal solution of the call admission control and routing problem in multi-service loss networks, in terms of average reward per time unit, is possible by modeling the network behavior as a Mar ...
TL;DR: This study shows that a very promising traffic grooming strategy is the one that deploys a sophisticated capacity installation algorithm in combination with the idea of charging the IP/MPLS layer for the capacity it consumes in the optical layer.
Abstract: Traffic grooming in meshed optical networks is an important research topic due to the vast difference between the bandwidth requirements of IP/MPLS traffic demands and the capacity of a wavelength. In this paper, we present, evaluate and compare several traffic grooming strategies for a multi-layer IP/MPLS-over-meshed optical network, which take into account the unidirectional nature of IP. Applying a proper multi-layer grooming algorithm also implicates designing a cost-efficient IP/MPLS topology suited for the offered traffic. This study shows that a very promising traffic grooming strategy is the one that deploys a sophisticated capacity installation algorithm in combination with the idea of charging the IP/MPLS layer for the capacity it consumes in the optical layer. Such an iterative, charging-based approach allows significant savings in the overall network design cost compared to a more simple approach. It also allows gradually installing extra line-systems in the optical network as traffic increases. Copyright © 2005 AEIT.
TL;DR: This paper develops and analyze a much simpler approach that is based on zero-forcing adaptation techniques and finds LMS-like performance is found to be within reach at a fraction of the cost of LMS.
Abstract: Digital data receivers often operate at a fixed sampling rate 1/Ts that is asynchronous to the baud rate 1/T. A digital equalizer that processes the incoming signal will also be asynchronous, and its adaptation is commonly based on extensions of the LMS algorithm. In this paper, we develop and analyze a much simpler approach that is based on zero-forcing adaptation techniques. Numerical results for an idealized optical recording channel serve to illustrate the merits of the approach. LMS-like performance is found to be within reach at a fraction of the cost of LMS. Copyright © 2004 AEI.
TL;DR: A self-organising protocol for Bluetooth topology construction in which scatternet structures are maintained even in the presence of dynamic perturbation of network configuration, which uses a bottom-up approach.
Abstract: We propose a self-organising protocol for Bluetooth topology construction in which scatternet structures are maintained even in the presence of dynamic perturbation of network configuration. The protocol does not require the presence of a central topology construction or re-construction process. Instead, the nodes can self-organise to create a stable configuration both after start-up as well as after intermediate changes due to the arrival of new nodes or shutting down of existing nodes. The proposed algorithm uses a bottom-up approach, which is built into the regular operations of the Bluetooth devices. Isolated nodes as well as masters and slaves of existing piconets can discover other nodes, thus extending the scatternet. Copyright © 2005 AEIT.
TL;DR: The diffusion approximation and the singular perturbation method are used in this paper to calculate the mean time to lose lock (MTLL) of the noncoherent digital delay lock loops.
Abstract: Noncoherent digital delay lock loops (DDLL) are suited for chip timing synchronisation in band-limited direct-sequence spread-spectrum (DSSS) demodulators. The diffusion approximation and the singular perturbation method are used in this paper to calculate the mean time to lose lock (MTLL) of the DDLL. Loop bandwidth optimisation for first order loop with severe Doppler is presented. A simple design rule for the loop bandwidth and a systematic approach for the loop threshold calculation are presented. Copyright © 2005 AEIT.
TL;DR: A reinforcement-leaming-based self-organisation scheme for cell configuration in multimedia mobile networks, which takes into account both pilot power allocation and call admission control mechanisms is proposed.
Abstract: In future wireless code division multiple access (WCDMA) cellular networks, random user mobility and time-varying multimedia traffic activity make the system design of coverage and capacity become a challenging issue. To utilise radio resource efficiently, it is crucial for cellular networks to have the capability of self-organisation for cell configuration, which can configure service coverage and system capacity dynamically to balance traffic loads among cells by being aware of the system situation. This paper proposes a reinforcement-leaming-based self-organisation scheme for cell configuration in multimedia mobile networks, which takes into account both pilot power allocation and call admission control mechanisms. Simulation results show that the proposed scheme improves system performance significantly compared to the conventional fixed pilot power allocation scheme and the scheme in which only pilot power is adjusted dynamically but the criterion of he call admission control is not coupled to it. Copyright if'') 2005 AEIT.
TL;DR: In this paper, it is shown how to obtain a performance characteristic, namely the information processing characteristic (IPC) introduced in Reference 15 for concatenated coding schemes, and how the IPC can be used to estimate the resulting bit error rate for the concatenation coding scheme.
Abstract: Asymptotical analysis of concatenated codes with extrinsic information transfer (EXIT) charts 3 or the analysis of multiple concatenations algorithm (AMCA) 17 is proven to be a powerful tool for the design of power-efficient communication systems. But, usually the result of the asymptotical analysis is a binary decision, whether convergence of iterative decoding is possible at the chosen signal-to-noise ratio, or not. In this paper, it is shown how to obtain a performance characteristic, namely the information processing characteristic (IPC) introduced in Reference 15 for concatenated coding schemes. If asymptotical analysis is performed under the assumption of infinite interleaving and infinitely many iterations, this IPC will be a lower bound. But, it is also possible to estimate a realistically achievable performance by restricting the number of iterations. Finally, the IPC can be used to estimate the resulting bit error rate for the concatenated coding scheme. As an upper and a lower bound on the bit error rate for a given IPC exist, we are able to lower bound the performance of any concatenated coding scheme and give an achievability bound, i.e. it is possible to determine a performance that can surely be achieved if sufficiently many iterations are performed and a large interleaver is used. Copyright © 2005 AEIT.
TL;DR: A non-matrix inversion based algorithm to implement decorrelating detection (DD), namely quasi-decorrelating detector (QDD), which uses truncated matrix power expansion instead of inverted correlation matrix to overcome the problems associated with the inversion transformation in DD.
Abstract: This paper proposes a non-matrix inversion based algorithm to implement decorrelating detection (DD), namely quasi-decorrelating detector (QDD), which uses truncated matrix power expansion instead of inverted correlation matrix to overcome the problems associated with the inversion transformation in DD, such as noise enhancement, computational complexity and matrix singularity etc. Two alternative QDD implementation schemes are presented in this paper; one is to use multi-stage feed-forward filters and the other is to use an nth order single matrix filter (neither involves matrix inversion). In addition to significantly reduced computational complexity, if compared with DD, the QDD algorithm offers a unique flexibility to trade among multiple access interference (MAI) suppression, near-far resistance and noise enhancement according to varying system set-ups. The obtained results show that the QDD outperforms decorrelator in either additive white Gaussian noise (AWGN) or multi-path channel, if the number of feed-forward stages is chosen properly. This paper also studies the impact of correlation statistics of spreading codes on the QDD's performance with the help of a performance-determining factor derived in this paper, which offers a code-selection guideline for the optimal performance of the QDD algorithm. Copyright © 2004 AEI.