waashk/dblp huggingface dataset:
lattice reduction aided multi-user mimo successive interference cancellation combined with linear pre-equalization. we present a lattice reduction (lr) aided successive interference cancellation (sic) scheme combined with linear pre-equalization in the correlated multi-user mimo system. the lr-aided sic schemes have been extensively studied to detect multiple users' symbols due to the nearly optimal performance. however, the lr algorithm and the sequential detecting method inherently incur considerable computational complexity overhead although it is of a polynomial order. to reduce their computational complexities, we decouple the entire system into multiple lower dimensional subsystems using linear pre-equalization based on the correlation among the users. we then utilize the lr-aided sic parallel in each subsystem. furthermore, to combine the lr-aided sic with pre-equalization optimally, we modify the lr-aided sic scheme, handling the residual interferences after pre-equalization.
an improved split-row threshold decoding algorithm for ldpc codes. we present an improved thresholding ldpc decoding algorithm which outperforms the split-row and original split-row threshold decoders with a small increase in hard-ware. simulation results show that the algorithm provides 0.27- 0.50 db coding gain over split-row, 0.10-0.20 db over split-row threshold, and is within 0.08-0.13 db of spa. compared with the original threshold algorithm the check node processor's gate count is increased by 3% while total chip area is kept the same.
on the security performance of physical-layer network coding. physical-layer network coding (plnc) is a novel wireless communication technology, in which multiple transmitters can send signals on the same channel to the same receiver at the same time. our previous studies have revealed that plnc can substantially improve the throughput performance of the whole network. in this paper, we address the security performance of plnc. in particular, we investigate the symbol error performance of a potential eavesdropper in the plnc system. extensive simulation studies show that plnc can provide security means against passive eavesdroppers.
the spatial effect of mobility on the mean number of handoffs: a new theoretical result. the mean number of handoffs is a fundamental performance measure in any mobile system, as it directly relates to the signaling load in the network as well as to the delivered qos. as the mobile services are evolving from simple cellular voice calls towards media and data sessions, and as cellular providers are reinventing their businesses by incorporating third party services, the handoff rate will even play a more pivotal role. this is because future sessions are expected to last longer than voice calls and users are more likely to roam into other networks. existing results provide an estimate of the mean number of handoffs in networks composed of an infinite number of access gateways and hence consider neither the topological arrangement of the gateways nor the mobility patterns between them. in this paper, we obtain a closed form solution for the mean number of handoffs under generic assumptions of two-dimensional markovian mobility patterns, spatial arrangement of the access gateways, as well as generic session times and gateway residence times. our solution unveils a new insight into mobility foundations as it shows that the consideration of the mobility pattern and the access gateways' layout simply transforms the known equation for the mean number of handoffs of an infinite network size from scalar to vector representation. we demonstrate that the mean number of handoffs is a non-linear function of the gateway spatial arrangement and user mobility.
a multicost approach to online impairment-aware rwa. we design and implement a multicost impairment-aware routing and wavelength assignment algorithm for online traffic. in transparent optical networks the quality of a transmission degrades due to physical layer impairments. to serve a connection, the proposed algorithm finds a path and a free wavelength (a lightpath) that has acceptable signal quality performance by estimating a quality of transmission measure, called the q factor. we take into account channel utilization in the network, which changes as new connections are established or released, in order to calculate the noise variances that correspond to physical impairments on the links. these, along with the time invariant eye impairment penalties of all candidate network paths, form the inputs to the algorithm. the multicost algorithm finds a set of so called non-dominated q paths from the given source to the given destination. various objective functions are then evaluated in order to choose the optimal lightpath to serve the connection. the proposed algorithm combines the strength of multicost optimization with low execution time, making it appropriate for serving online connections.
performance-aware security of unicast communication in hybrid satellite networks. in this work, we address the performance problems that arise when unicast security protocols ipsec and ssl are applied for securing the end-to-end communication in hybrid satellite networks. satellite networks use tcp and http performance-enhancing proxy servers to overcome the adverse effect of the large delay-bandwidth product of the satellite channel. however, the proxy servers cannot function when ipsec and ssl are used for secure unicast communication in hybrid satellite networks. we therefore propose the use of the layered ipsec (les) protocol as an alternative to ipsec for network-layer security. we describe a modification to the internet key exchange protocol if dynamic key establishment is needed for layered ipsec. for application-level security of web browsing with acceptable end-to-end delay, we propose the dual-mode ssl protocol (dssl) to be used instead of ssl. we describe how les and dssl protocols achieve the desired end-to-end communication security while allowing the tcp and http proxy servers to function correctly. through simulation studies, we quantify the improvement in performance that is achieved using our proposed protocols, compared to traditional ipsec and ssl.
capacity of optical intensity channels with peak and average power constraints. the design and analysis of capacity-approaching input signalling for optical intensity channels are presented. both peak and average optical power constraints are considered in the analysis. the capacity-achieving distribution for this channel is discrete with a finite number of mass points. in practice, finding this distribution requires solving a complex non-linear optimization at every snr. in this work, we present a closed form discrete capacity-approaching distribution derived via source entropy maximization. the computation of this distribution is substantially less complex than previous optimization approaches and can be easily computed for different snrs. the information rates using the derived maxentropic distribution are shown to be negligibly far away from the channel capacity found by non-linear optimization in the snr range -6 to 6 db.
bandwidth-guaranteed multicast in multi-channel multi-interface wireless mesh networks. we consider multi-channel multi-interface wireless mesh networks with a schedule-based mac protocol, where conflict-free transmission is ensured by requiring links assigned with the same channel and within the mutual interference range of each other to be active at different time slots. when a (point-to-multipoint) multicast call arrives, the call is accepted if a multicast distribution tree can be established for connecting the source node with all the receiving nodes, and with sufficient bandwidth reserved on each link. otherwise, the call is rejected. to maximize the call acceptance rate, the multicast tree must be constructed judiciously upon each call arrival. aiming at minimizing the carried load on the most-heavily loaded channel, and maximizing the residual capacity of the most heavily loaded node, an integer linear program (ilp) is formulated for multicast tree construction. since solving ilp can be time-consuming, an efficient heuristic algorithm is then proposed. we compare the two tree construction algorithms by simulations. we found that both algorithms give comparable call acceptance rate, but the heuristic algorithm requires much shorter running time.
measurement-based modeling of vehicle-to-vehicle mimo channels. vehicle-to-vehicle (vtv) communications are of interest for applications within traffic safety and congestion avoidance, but the development of suitable communications systems requires accurate models for vtv propagation channels. this paper presents a new wideband mimo (multiple-input-multiple-output) channel model for vtv channels based on extensive mimo channel measurements performed at 5.2 ghz in rural environments in lund, sweden. the measured channel characteristics, in particular the non-stationarity of the channel statistics, motivate the use of a geometry-based stochastic channel model (gscm) instead of the classical tapped-delay line model. we introduce generalizations of the generic gscm approach and find it suitable to distinguish between diffuse and discrete scattering contributions. the time-variant contributions from discrete scatterers are tracked over time and delay using a high resolution algorithm, and our observations motivate their power being modeled as a combination of a deterministic part and a stochastic part. the paper gives a full model parameterization and the model is verified by comparison of mimo antenna correlations derived from the channel model to those obtained directly from measurements.
tri-message: a lightweight time synchronization protocol for high latency and resource-constrained networks. existing terrestrial synchronization protocols including rbs, ftsp, tpsn, lts and tshl have already achieved high precision in radio networks, but none of them perform well in high latency networks like acoustic sensor networks. in this paper, we present tri-message: a lightweight time synchronization protocol for high latency and resource-constrained networks. as its name suggests, only three message exchanges are required in one synchronization process. meanwhile, tri-message utilizes very simple mathematical operations to calculate the clock skew and offset. specially, tri-message is feasible for many extremely long latency applications such as space exploration because it has an increasing synchronization precision with the increasement of distance.
an upper bound on the performance of non-repetitive flooding over csma in wireless ad-hoc networks. although flooding and its variants are widely deployed for broadcasting by different applications, there are limited results on a complete and comprehensive analytical framework describing their behavior in general cases. we have previously published results which provide an upper bound for the performance of flooding when flooded packets have the highest serving priority. in this paper, using a different and simpler approach, we develop an analytical framework for analysis of flooding in general cases where flooding packets do not receive any special priority treatment in the network. the analysis is performed for a static multi-hop ad hoc wireless network using csma as its mac layer. the framework provides an upper bound on the network coverage and energy consumption of flooding and its popular variant, probabilistic flooding for any service time and queuing delay that flooded packets experience. the analytical upper bound is verified by extensive simulations which give evidence of its tightness in real scenarios.
on contextcast: a context-aware communication mechanism. the dissemination of messages according to clients' contexts (i.e., location and other attributes) opens up new possibilities in context-aware systems. while geocast or content-based publish/subscribe forward messages according to client location or attributes, respectively, neither uses a combination of the two. in this paper, we present this new communication paradigm and the challenges it poses. we also extend concepts from publish/subscribe networks to efficiently deal with highly dynamic user location to lower update rates by approximating the user's location. this reduces update rates by between 25% and 90%, depending on the granularity of the approximation.
information hiding with optimal detector for highly correlated signals. in this paper, a novel scaling based information hiding approach robust against noise and gain attack is presented. the host signal is assumed to be stationary gaussian modeled with a first-order autoregressive process. for data embedding, the host signal is divided into two parts. one part is manipulated while the other part is kept unchanged for parameter estimation. the decoding scheme using the ratio of samples is suitable for highly correlated signals in which the decoding process is difficult. by calculating the distribution of the ratio, the performance of the maximum likelihood decoder is analytically studied. the proposed algorithm is applied to several artificial gaussian autoregressive signals to verify the validity of our results.
joint path and wavelength selection using q-learning in optical burst switching networks. contention losses which usually do not indicate congestion is a major issue that hinders the deployment of optical burst switching (obs) networks. development of efficient path and wavelength selection algorithms is crucial to minimize the burst loss probability (blp) in obs networks. in this paper, we handle path selection and wavelength selection in a joint fashion. we formulate the problem of selecting a pair of path and wavelength jointly as a multi-armed bandit problem (mabp) and discuss the difficulties in solving mabp directly. we then rewrite the q-learning formalism to solve the mabp without explicit model in an online fashion and propose an algorithm to solve the problem near-optimally. the proposed algorithm selects a pair of path and wavelength at each ingress node to minimize the blp on the long run. simulation results demonstrate the effectiveness of our algorithm in minimizing the blp with better link utilization compared to the other proposals in the literature.
channel access throttling for overlapping bss management. multiple co-channel wlan bsses (i.e., wlan cells) overlapping in coverage are generally considered undesirable because members of the obsses compete for channel access, which typically increases the contention level of wireless medium access and reduces overall system performance. in this paper, we propose to use channel access throttling (cat) for managing wireless lan radio resources for overlapping bsses (obsses). cat provides an access point (ap) of each bss with a mechanism to control channel access parameters of its member stations on the fly. by coordinating the cat operations of the obss aps, we can enable privileged channel access to an individual bss at a particular time, for example, by assigning high priority access parameters to member stations associated with the bss. by controlling how much each bss may be given the privileged channel access, we can also achieve a proportional partitioning of channel capacity among obsses. we present evaluation results obtained from both simulations and experiments using testbed built with commercial off-the-shelf (cots) wlan hardware and open-source device driver. our results show that with cat, not only can we proportionally partition channel capacity among the obsses, but also improve channel utilization efficiency and increase overall capacity.
efficient adaptive routing in delay tolerant networks. conventional routing algorithms in mobile ad hoc networks (manets), i.e., multi-hop forwarding, assume the existence of contemporaneous source-destination paths and are not scalable to large networks. on the other hand, in delay tolerant networks (dtns), routing protocols use the mobility-assisted, store-carry-forward paradigm which allows delivery among disconnected network components. adaptive routing, which combines multi-hop and mobility-assisted routing protocols, is of practical value: it allows efficient multi-hop forwarding while providing the flexibility to deliver messages among disconnected network components. however, existing adaptive routing protocols use mobility-assisted routing protocols as an alternative only when the former fails. in this paper, we propose to improve the performance of adaptive routing from a resource allocation point of view, in situations where bandwidth is a critical and limited resource affecting routing performance. we propose an adaptive routing protocol, named efficient adaptive routing (ear), which allocates bandwidth (or forwarding opportunities) between its multi-hop forwarding component and its mobility-assisted routing component dynamically to improve bandwidth utility. simulations are conducted to evaluate the routing performance of ear under different network parameters.
optimal transmission for dying channels. in this paper, we investigate the optimal transmission schemes for dying channels, which were introduced in [1]. the dying channels are resulted in wireless networks subject to random fatal impacts, e.g., sensor networks under sudden physical attacks or cognitive radio networks with unpredictable primary user occupancy. due to the non-ergodic and delay-limited nature of a dying channel, the outage capacity is adopted as the performance metric. firstly, we show that the optimal power allocation profile is non-increasing when fading gains are independently and identically distributed (i.i.d.). secondly, when the fading gains over the blocks are the same, we prove that the optimal number of blocks over which a codeword should be spanned is k = 1. at last, we consider the case where uniform power allocation is utilized and fading gains are i.i.d. in this case, we derive the upper and lower bounds for the outage probability. moreover, for the high signal-to-noise ratio (snr) case with rayleigh fading , we derive analytical results on the optimal number of coding blocks k. for the low snr case, we show that repetition transmissions are approximately optimal.
fast power control for cross-layer optimal resource allocation in ds-cdma wireless networks. this paper presents a novel cross-layer design for joint power and end-to-end rate control optimization in ds-cdma wireless networks, along with a detailed implementation and evaluation in the network simulator ns-2. starting with a network utility maximization formulation of the problem, we derive distributed power control, transport rate and queue management schemes that jointly achieve the optimal network operation. our solution has several attractive features compared to alternatives: it adheres to the natural time-scale separation between rapid power control updates and slower end-to-end rate adjustments, and uses simplified power control mechanisms with reduced signalling requirements. we argue that these features are critical for a successful real-world implementation. to validate these claims, we present a detailed implementation of a cross-layer adapted networking stack for ds-csma ad-hoc networks in ns-2. we describe several critical issues that arise in the implementation, but are typically neglected in the theoretical protocol design, and evaluate the alternatives in extensive simulations.
link adaptation in linearly precoded closed-loop mimo-ofdm systems with linear receivers. upcoming multi antenna systems such as 3gpp- lte employ code book based multi-mode precoding in order to adapt to a wide range of channel conditions. link adaptation, which includes the selection of precoding matrices, the number of spatially multiplexed layers as well as modulation coding schemes is a crucial task, carried out by the receiver. in this contribution we propose link adaption based on the measure of mutual information between the channel input and the linear detector output and evaluate the behavior of the proposed algorithm in spatially correlated and uncorrelated propagation scenarios. the results highlight the importance of proper link adaption in order to mitigate the impact of spatial correlation.
statistical learning for automated rrm: application to eutran mobility. self organizing network (son) functionalities are currently developed to improve network performance and management tasks. son functionalities require efficient utilization of data extracted from the network. in this context, the paper has two objectives. first it is shown that one can use simple statistical learning techniques such as regression to extract a model from data. the model comprises closed form expressions that approximate the functional relations between measured key performance indicators (kpis) and radio resource management (rrm) parameters. second, it is shown how the model can be integrated in a monitoring process and be used to devise an efficient auto-tuning algorithm. to this end, two case studies of handover monitoring and handover auto-tuning in a lte network are described and illustrate the application of the proposed approach.
dual hop mimo relaying with orthogonal space-time block codes. this paper considers orthogonal space-time block coded (ostbc) transmission for non-regenerative multiple-input multiple-output dual-hop channels. we focus on scenarios where the relay does not have access to instantaneous channel state information, and as such operates according to a non-coherent amplify-and-forward protocol based on a long-term power constraint.we investigate the performance of the proposed ostbc approach by employing tools from finite-dimensional random matrix theory. in particular, we derive exact closed-form expressions for the moment generating function, high order cumulants, and first and second moments of the signal-to-noise ratio at the destination. based on these results, we also derive analytical expressions for the symbol error rate with m-ary phase-shift keying, and the amount of fading.
error-tolerant searchable encryption. in this paper, we describe a new primitive for error-tolerant searchable encryption and a security model for it. this generic scheme permits to make searches on encrypted data with only an approximation of some keyword. it enables to efficiently query secure databases in order to get the exact data with a close estimation of it. an application to biometric identification arises from this construction. this is the first construction both for error-tolerant searchable encryption and for a biometric identification protocol over encrypted personal data.
optimal output back-off in ofdm systems with nonlinear power amplifiers. a well-known problem of ofdm signals is their high peak-to-average power ratio, which can cause the clipping of peaks in the transmitted signal due to the limited linear range of high power amplifiers. operating the amplifier solely in the linear region, i.e., with a large output back-off, results in an undistorted transmitted signal, but at the expense of a low snr at the receiver. driving the amplifier into saturation, on the other hand, maximizes the received snr, but causes severe nonlinear signal distortions. in this paper we study the resulting trade-off. we show both theoretically and by simulations that, despite the distortions, it is optimal to operate the amplifier close to saturation. furthermore, we analytically derive a modification of the bussgang noise cancellation algorithm which was recently shown in the literature to improve the exit characteristic of the algorithm.