We address the problem of video-aware multiuser resource management in modern wireless networks such as 3GPP Long Term Evolution (LTE) in the context of video delivery systems like HTTP Adaptive Streaming (HAS). HAS is a client driven video rate adaptation and delivery framework that is becoming popular due to its inherent advantages over existing video delivery solutions. Quality of Experience (QoE) is the prime performance criterion for adaptive video streaming and wireless resource management is a critical part in providing a target QoE for video delivery over wireless systems. However modifying resource management functionality to be video-aware at the network edge is rather difficult in practical networks. In this paper, we propose an alternative architecture to enhance video QoE in QoS (Quality of Service)-aware networks wherein the intelligence for video aware resource management resides at the network-core rather than at the network edge. In this new architecture, a "Video Aware Controller" (VAC) is placed at the network core. The VAC periodically receives HAS-related feedback from adaptive streaming clients/servers which it converts to QoS parameters for each user. Further, we propose an algorithm to dynamically compute the Maximum Bit Rate (MBR) for each streaming user based on media buffer feedback. Our simulation results on an LTE system level simulator demonstrate significant reduction in re-buffering percentage and enhanced QoE-outage capacity compared to existing schemes.

We formulate a PHY/APP cross-layer resource allocation problem for efficient transmission of video streams in a multiple-user LTE downlink system. To achieve a predetermined video PSNR, the number of bits needed for different users is calculated using a parameterized Rate-Distortion (RD) model proposed by [4]. We design an admission policy which assigns frequency-time OFDMA channel resource to video users based on a cross layer metric. For the admitted users, we use a tracking algorithm to serve the users as the video source content and channel conditions evolve. The goal of the resource allocation is to maximize the number of admitted users from a fixed user population and guarantee that the video quality of admitted users will achieve the predetermined PSNR threshold. The performance of the proposed algorithms is compared to four baseline algorithms which exploit different levels of cross layer knowledge about the channel and source characteristics, and the results show benefits from cross-layer optimization.

The 19 papers in this special issue focus on the push beyond giga-bit-per-second (Gbps) data rates, in order to more rapidly access data on personal devices, as well as potentially replace all the cables going into a device, including the video cable. This issue beings together the state-of-the-art, across multiple disciplines, for achieving Gbps WPAN capability.

We propose a MAC protocol for use in multihop wireless networks that deploy an underlying UWB (ultra wide band)-based physical layer. We consider a multiband approach to better utilize the available spectrum, where each transmitter sends longer pulses in one of many narrower frequency bands. The motivation comes from the observation that, in the absence of a sophisticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by the delay spread of the channel. Therefore, using a wider frequency band to shorten the transmission time for each pulse does not increase the data rate in proportion to the available bandwidth. Our approach allows data transmissions to be contiguous and practically interference free, and, thus, highly efficient. For practicality, we ensure the conformance of our approach to FCC-imposed emission limits. We evaluate our approach via extensive simulations, and our results demonstrate the significant advantages of our approach over single-band solutions: the throughput increases significantly and the number of collisions decreases considerably. Finally, we analyze the behavior of our MAC protocol in a single-hop setting in terms of its efficiency in utilizing the multiple bands

Abstract Ultra wide band (UWB) technology offers a promising high capacity solution for short‐range wireless ad hoc networks, as in home networks or in wearable ad hoc networks. In this paper, we propose a novel multi‐band MAC protocol for use in small ad hoc networks that deploy an underlying UWB based physical layer. In our approach, we divide the available UWB bandwidth into multiple simultaneously usable bands. In the absence of a sophisticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by thedelay spreadof the channel. Therefore, using a wider frequency band to shorten the transmission time for each pulse does not increase the data rate in proportion to the available bandwidth. A multi‐band approach that uses a plurality of bands that adhere to FCC specifications, with slightly elongated pulse durations, provides a solution that can effectively utilize the UWB spectrum. Our approach is based on the idea of conflict resolution using binary ‘something’/‘nothing’ feedback, which has not been widely studied in wireless and specifically in UWB networks. Our protocol unites binary conflict resolution and multi‐band utilization to effectively utilize the available bandwidth. To ensure that our proposed approach is tightly knit with the underlying physical layer, we discuss physical–layer dependencies and the conformance to FCC‐imposed emission limits. We evaluate our approach via extensive simulations. Our simulation results demonstrate the significant advantages of our approach over single‐band solutions: the throughput increases significantly, and the number of collisions decreases considerably. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract — Ultra Wide Band (UWB) technology offers a promising high capacity solution for wireless networks with short-range links. However, MAC and higher-layer ad hoc network protocols that exploit the UWB technology are yet to mature. In this paper, we propose a MAC protocol for use in multi-hop wireless networks that deploy an underlying UWB based physical layer. We adopt a multi-band approach wherein we divide the available UWB bandwidth into multiple simultaneously usable bands. The motivation comes from the following observation: in the absence of a sophisticated equalizer, the size of a slot for transmitting a UWB pulse is typically dictated by the delay spread of the channel. Therefore, using a wider frequency band to shorten the transmission time for each pulse may not increase the data rate in proportion to the available bandwidth. Thus, we consider a multi-band approach to better utilize the available spectrum, where each transmitter sends longer pulses in one of many narrower frequency bands. Unlike previous single hopped schemes that rely on timehopping, our approach allows data transmissions to be contiguous, and thus, highly efficient. The approach also ensures that data communications are practically interference free and are only subject to thermal noise effects. To ensure that our proposed approach is tightly knit with the underlying physical layer, we discuss physical-layer dependencies and the conformance of our approach to FCC-imposed emission limits. We evaluate our approach via extensive simulations. Our simulation results demonstrate the significant advantages of our approach over single-band solutions: the throughput increases significantly, and the number of collisions decreases considerably.

The paper provides a tutorial overview of ultrawideband (UWB) radio technology for high-speed wireless connectivity. Subsequent to establishing a historical and technological context, it describes the new impetus for UWB systems development and standardization resulting from the FCC's recent decision to permit unlicensed operation in the 3.1-10.6 GHz band subject to modified Part 15 rules and indicates the potential new applications that may result. Thereafter, the paper provides a system architect's perspectives on the various issues and challenges involved in the design of link layer subsystems. Specifically, we outline current developments in UWB system design concepts that are oriented to high-speed applications and describe some of the design tradeoffs involved.

The performance of a RAKE receiver for a pulse based ultra-wideband (UWB) communications system is studied in a realistic channel model that is based on an extensive set of indoor channel measurements. The RAKE receiver is shown to contribute to a mitigation of the ISI. In particular, at low input SNR values and small number of RAKE taps, it is shown that employing additional RAKE taps for energy capture is more important to overall system performance than employing equalization to combat the ISI. The performance of the RAKE with some realistic channel estimation errors is also studied.

Due to the inherent overlay nature of ultrawideband (UWB) systems, it is important to understand and quantify the potential interference caused to narrowband systems that may be located within the bandwidth of the UWB waveform. The simplest way to treat UWB interference is to model it as additive, white Gaussian noise within the bandwidth of the narrowband receiver. However, previous experiments showed that the interference of UWB systems is a function of many factors, including the modulation used, the pulse repetition frequency, the center frequency of the "narrowband" system, and the structure of the "narrowband" receiver. This paper quantifies the effect that a UWB interferer has on the bit error probability of a generic "narrowband" system in order to determine the applicability of the white, Gaussian noise model. These results can also be used to help properly design a UWB system that causes minimal interference to known, overlayed narrowband systems.

Systems using ultra-wideband (UWB) technology have been shown to achieve very high data rates (100 Mbps and above) for short-range, indoor applications. UWB signals exhibit a number of performance advantages in terms of multipath resolution and fading reduction. However, UWB systems can also exhibit significant implementation complexity in timing, synchronization, and signal correlation. This paper presents a differential detector that rakes in some of the multipath energy, while relaxing some of the stringent implementation requirements. We analyze the performance and the implementation of the differential detector, and compare it to a RAKE receiver with a correlator detector in the presence of AWGN and multipath.

The IEEE 802.16.1 Task Group is developing PHY and MAC protocols as part of the LAN/MAN series of standards. Issues related to standards development for LMDS are discussed. Solutions incorporated into the current set of baseline documents are described, along with rationale for their inclusion.

This paper analyzes the performance of a convolutionally coded code-division multiple-access system, which employs a linear, minimum mean-square error (MMSE) receiver for interference suppression. A flat, Rayleigh fading channel is considered, where convolutional encoding and interleaving are employed in order to combat the effects of the fading. Theoretical results are derived for the average bit-error probability of the MMSE receiver, where the optimum tap weights for the adaptive filter are determined by the solution of the Wiener-Hopf equations. Simulation results showing the average bit-error rate of the MMSE receiver are also presented, which incorporate the effects of recursive least squares adaptation, channel estimation using pilot symbol-assisted modulation, and finite interleaving. Results show that the MMSE receiver with coding can provide a substantial gain over the matched-filter receiver in a rapidly varying, Rayleigh fading channel. The results also reiterate the fact that lower rate codes are not necessarily the best choice when used with the MMSE receiver.

Previous results have shown that high rate codes tend to yield a lower average bit-error rate than low rate codes when employing a minimum mean-square error (MMSE) receiver for a direct-sequence code-division multiple-access (CDMA) system in either an additive white Gaussian noise channel or a flat Rayleigh fading channel. we consider the use of larger signal constellations with both trellis-coded modulation and bit-interleaved coded modulation (BICM) to determine if further gains can be achieved in either the Rayleigh or Ricean fading channel. The average bit-error probability is derived for both coding schemes using the general Ricean fading channel model, based upon the common assumptions of infinite interleaving, perfect channel state information, and optimal MMSE receiver coefficients. New bounds are presented for BICM with 8-PSK and 16-QAM symbols, which take advantage of the symmetries inherent in the signal constellations with Gray code mapping. In addition, simulation results are presented which show the important effect a finite interleaving delay constraint has on the comparison of various codes. The results show that there are cases when coded modulation does yield a significant improvement in performance for a CDMA system using an MMSE receiver, compared to standard convolutional coding. However, the best coding strategy depends upon several factors, including the nature of the fading process (Rayleigh or Ricean), the operating signal-to-noise ratio, the interleaving delay constraint, the time-variability of the channel, the number of users in the system, and the severity of the near-far problem.

This paper extends the analysis presented by Eng and Milstein (see IEEE J. Select. Areas Commun., vol.12, no.5, p.938-951, 1994) of a hybrid frequency division multiple access/code-division multiple-access [FDMA/CDMA (F/CDMA)] system in a Rayleigh fading environment to include the presence of a direct-path component (i.e., Ricean fading). The results show that a "wideband" CDMA system out performs a hybrid system, although the combination of a specular component and an exponentially decaying multipath intensity profile (MIP) with a large decay factor may result in only a minimal degradation of system performance for a hybrid system.