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.
Code-division multiple-access (CDMA) has the potential to support traffic sources with a wide range of quality of service (QoS) requirements. The traffic carrying capacity of CDMA channels under QoS constraints (such as delay guarantee) is, however, less well-understood. In this work, we propose a method based on stochastic network calculus and large system analysis to quantify the maximum traffic...
In this paper, we propose an adaptive single-carrier (SC) transmission suitable for near maximum likelihood (ML) block signal detection using QR decomposition and M-algorithm (QRM-MLBD). QRM-MLBD can significantly improve the bit error rate (BER) performance of SC block transmission. However, in order to achieve a close-to-ML performance, the use of a fairly large number M of surviving paths in the...
This paper analyzes the exact average symbol error rate (SER) performance of beamforming in spatially correlated multiple-input single output (MISO) systems with channel estimation error and feedback delay. We derive the joint distribution function of two quadratic forms and employ the result to obtain an expression for the cumulative distribution function (cdf) of the received signal-to-noise ratio...
We investigate the use of the minimum mean-squared- error decision-feedback-equalizer (MMSE-DFE) as a preprocessor to reduce the computational complexity of symbol detection in frequency-selective multiple- input multiple-output (MIMO) channels. The preprocessor delays and focuses the received signal energy which reduces the effects of inter-symbol- interference and multiple-access-interference. This...
In this paper, the performance of adaptive modulation for multiuser amplify-and-forward relay networks over Nakagami-$m$ fading is studied. Specifically, adaptive discrete rate five-mode $M$-ary quadrature amplitude modulation is employed with fixed switching thresholds. In particular, the detrimental effect of feedback delays in multiuser scheduling is quantified. To this end, an upper bound of the...
Incremental relaying (IR) is known to improve the spectral efficiency of cooperative communication by using the destination feedback. In IR, the relay nodes are employed to assist the source transmission only if it is failed. When the relay nodes perform demodulate-and-forward (DmF), all of them are eligible to forward the source information. This is different from decode-and-forward (DF), where only...
Pricing plays a crucial role in trading any resource or service in the existing Broadband Wireless Access system i.e. WiMAX. Through a proper pricing strategy, a wireless service provider would like to achieve the highest revenue, while the end users would like to achieve the highest satisfaction from service usage. In order to make it feasible, in this paper we propose a tradeoff policy between the...
Water channels can be observed in different applications: management of drinking water, sewer system, copper mining industry etc. In particular their study is relevant for agriculture where improved water level control and reduced losses due to perturbations (such as water off-takes) is increasingly relevant when facing more frequent droughts. A particular challenge when dealing with water canals...
This paper investigates the beamforming design for multiuser downlink with limited feedback, where a practical channel state information (CSI) feedback model consisting both feedback delay and CSI quantization error is considered. Under this circumstance, we derive a closed-form multiuser beamforming scheme via minimizing the expected mean square error (MSE) with respect to the feedback imperfection...
Modern speech coders utilize several models in sequence to encode a single frame. The typical sequence consists of a linear predictor for modeling short scale structure, adaptive codebook for mid to long scale structure, and algebraic codebook for the remainder. We develop an alternative model, termed the Complete Oscillator Model (COM), which encodes structures on multiple time scales at once. When...
Opportunistic Network Coding (ONC) has attracted much attention recently. The main improvement of ONC over the traditional network coding is that ONC allows the encoding node to decide whether it employs network coding based on the status of all its input streams. However, due to the nature of fading, wireless links may not always be reliable. Thus, the performance gain of ONC over traditional methods...
We show that the performance of relay selection can be improved by employing relays with buffers. Under the idealized assumption that no buffer is full or empty, the best source-relay and the best relay-destination channels can be simultaneously exploited by selecting the corresponding relays for reception and transmission, respectively. The resulting relay selection scheme is referred to as max-max...
This paper presents the design and implementation of a low power, low voltage, continuous time delta sigma modulator for audio band in 90 nm CMOS technology. A VCO-based integrator and quantizer are used. Inherent dynamic element matching (DEM) of the quantizer eliminates the need for explicit DEM logic which results in a short excess-delay and power saving. Simulation results show that the modulator...
The proposed resource allocation scheme can boost the spectral efficiency of multi-user OFDMA wireless systems with heterogeneous delay requirements. The existing designs usually have two important assumptions that the users are delay insensitive and Channel State Information at the Transmitter (CSI) is perfect. In practice, users have heterogeneous delay requirements and CSI usually becomes outdated...
In this paper, we analyze the performance of a dual- hop system with partial relay selection and feedback delay over Rayleigh fading channels in the presence of multiple identical interferers at the destination. Based on the new closed-form expressions for the cumulative distribution function of the effective signal-to-interference plus noise ratio, we present closed-form expressions for the outage...
We have been developing a minimum mean square error macro-diversity (MMSE-MD) reception system using distributed remote antennas and radio-on-fiber (RoF) links for use in live broadcasts of road races. For the system to be feasible, we have to consider the propagation delay differences among diversity branches due to RoF links and radio propagation. This paper describes a hardware implementation of...
In this paper, we propose a novel mobile optical wireless (OW) system that employs for the first time beam delay adaptation, and makes use of angle and power adaptation in a line strip multibeam spot diffusing configuration in conjunction with an imaging receiver (BDAPA-LSMS). Our ultimate goal is to improve the bandwidth, reduce the effect of inter-symbol-interference (ISI), and increase the signal...
In this paper, we study the data broadcast issue in wireless networks with directional antennas. We are given an Access Point(AP) and a set of clients served by the AP. Our task is to schedule the transmission of AP by using directional antennas such that the total delay for all clients to receive a broadcast packet is minimized. Directional antennas allow transmission energy to be concentrated on...
Transmitted-reference (TR) modulation schemes have generated interest in the context of ultrawide bandwidth (UWB) communications in order to avoid complex channel estimation and synchronization. In these schemes, the length of the integration interval must be carefully chosen to achieve optimal performance. Difficulties arise since this parameter is related to the channel characteristics and to the...
Long Term Evolution (LTE) is emerging as a major candidate for 4G cellular networks to satisfy the increasing demands for mobile broadband services, particularly multimedia delivery. MIMO (Multiple Input Multiple Output) technology combined with OFDMA and more efficient modulation/coding schemes (MCS) are key physical layer technologies in LTE networks. However, in order to fully utilize the benefits...
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.