The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The following topics are dealt with: modulation and coding; ad-hoc wireless networks; radio channel measurements and modeling; space-time coding; MIMO; radio resource management; QoS; resource allocation; cross-layer design; turbo codes; iterative decoding and processing and ultra wide-band communications.
This paper addresses a method to mitigate the peak to mean power ratio (PMEPR) of orthogonal frequency division multiplexing (OFDM) signals. The idea is to use adjacent bands of the OFDM spectrum to allocate optimized subcarriers so as to decrease the signal PMEPR with the help of SOCP optimization process. This way of doing has only sense if additional subcarriers all fall under the standard spectrum...
In this paper, we construct an elementary spatial-temporal routing scheme that achieves the throughput capacity of a large ad hoc wireless network with high probability as the number of nodes increases. We consider a multicast type of traffic handling using a hierarchical routing with clustering. We investigate the scaling of throughput capacity versus the number of nodes and destinations. The derived...
In this paper, we deploy a modified version of Shanno algorithm in order to optimize the bit error rate (BER) cost function using a nonlinear block optimization strategy for its minimization. The resulting algorithm is called the Block Shanno Minimum BER (BSMBER), which is conducted in the design of spatial multiuser receivers for orthogonal frequency division multiplexing (OFDM) system using multiple...
This paper studies the performance of orthogonal frequency division multiple access (OFDMA) in the multiuser multicarrier MIMO (M3) system for both uplink (UL) and down-link (DL) channels. We numerically quantify the performance gap between OFDMA and the optimal multicarrier solution. We also derive simple but near optimal algorithms to solve the generic OFDMA resource allocation problem in different...
In this paper, we present a new method to analyze the performance of automatic repeat request (ARQ) schemes in self-similar traffic for the future service-oriented Internet. Taking into account the self-similar traffic of a massive-scale wireless multimedia service, we build a batch arrival queueing model and suppose the batch size is a random variable following Pareto (c, alpha) distribution. Considering...
In this paper, we aim to provide an analytical modeling of cyclic delay diversity in an OFDMA based system. Cyclic delay diversity is a low complexity spatial diversity scheme where multiple transmit antennas transmit delayed versions the same signal. While CDD increases the frequency selectivity, the reduced coherence bandwidth resulted in higher requirements for the channel estimation at the receiver...
Cluster-based architectures are one of the most practical solutions in order to cope with the requirements of large-scale WSNs. In this work a new cluster-based architecture for sparse WSNs is introduced, the key issue of the solution presented is the multihop approach that is followed both in the communication from sensors to cluster-heads and from cluster-heads to the sink. Intercluster multihop...
Enhanced Uplink operation of WCDMA-UMTS systems utilizes fast Node B scheduling and a short Transmission Time Interval (TTI) of 2ms. The scheduling decisions are based on scheduling information (SI) sent by each UE to the Node B. The main drawback of the current scheduling procedure is that the SI does not include any information regarding the delay sensitivity of each traffic flow, as well as the...
This paper provides an overview of the methodology used in the performance assessment of the 64QAM and MIMO HSDPA features in a macro-cellular environment. The paper describes how the geometry experienced by end users could be measured in a live HSPA network, and how this could be used together with link level simulations to perform a first assessment of performance expectation of both MIMO and 64QAM.
OFDM (orthogonal frequency division multiplex) achieves high spectral efficiency in broadband wireless communications but has poor amplification efficiency due to its large peak-to-average power ratio. This paper presents achievable average power efficiency for the OFDM signal when the Doherty and extended Doherty transmitters are employed. By modelling the envelope of OFDM signal as a Rayleigh-distributed...
Low power medium access control (MAC) protocols have received a lot of attention in the last few years because of their impact on the lifetime of wireless sensor networks. Due to the cost of implementation on real hardware, and sometimes to a lack of detail in the description of these protocols, it is difficult to evaluate them. This paper describes the latest advances in the field and introduces...
The design of wireless sensor networks (WSNs) should focus on energy efficiency since wireless sensor nodes work on limited batteries, which are difficult or impossible to replace in most situations. However, the performance of WSNs is adversely impacted by fading effects, which requires much energy to combat for a high bit error rate (BER) requirement. On the other hand, since the transmit energy...
Passive RFID tags, which have no self-battery and just backscatter the energy from a reader, share a common channel. It causes a tag-to-tag collision problem when at least two or more tags communicate to the reader simultaneously. The dynamic frame slotted Aloha (DFS-Aloha) protocol is one of the well-known anti-collision algorithms to solve this problem. To maximize the system performance and enhance...
This paper presents a reduced-complexity cluster modeling method for channel models based on the 3GPP channel model to simulate the time variation of spatially correlated wideband MIMO channels. The main novelty is that, when modeling the time-variant wideband MIMO channels, instead of tracking the changes in the angles of arrival (AoAs) of all the multi-path components (MPCs) defined, we only track...
In this paper we evaluate the performance of our earlier proposed enhanced relay-enabled distributed coordination function (ErDCF) for wireless ad hoc networks. The idea of ErDCF is to use high data rate nodes to work as relays for the low data rate nodes. ErDCF achieves higher throughput and reduced energy consumption compared to IEEE 802.11 distributed coordination function (DCF). This is a result...
This paper presents an analysis method of i.i.d. (independent and identically distributed) MIMO (multiple input multiple output) channels under Nakagami m fading environment based on statistical distributions of the largest eigenvalue which is useful for the analysis of MRC (maximal ratio combining) communication systems. Given distribution formulae are introduced utilizing the conversion of MIMO...
Near optimum iterative decoding of block codes in multiple input multiple output (MIMO) systems is proposed and analyzed applying a new suboptimal space time soft input soft output detector and Chase Pyndiah decoder for FEC detection. The suboptimal space time detector applies zero forcing detection to estimate the center and radius of the hyper-sphere which determines a subset of the most probable...
Recently a new detection method for TR-UWB systems called time delayed sampling and correlation (TDSC) has been proposed. This new method overcomes the major difficulties in a traditional TR-UWB detection method based on a wide band delay line. TDSC is based on a time to space conversion realizable by an analog waveform sampler. In this paper a first prototype is presented designed using low cost...
In this paper, we propose an efficient ranging technique using chirp signal, which employs a matrix pencil method to estimate time of arrival (TOA). The proposed TOA estimation method consists of a two-step signal processing: minimum mean square error (MMSE)-based channel impulse response estimation and the channel delay tracking by matrix pencil algorithm. At the first step, the transmitted known...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.