Information Theory and Reliable Communication

Welcome to the second installment of IJBDCN. This issue contains three research papers and a comprehensive survey article on mobile ad hoc networks. We would like to publish a couple of survey or tutorial articles per year as we believe this to be of value to our readers. Many research papers are necessarily focused and do not allow for a " panoramic " view of a particular subject. This is the gap that well-written survey or tutorial papers can fill. We are also planning a guest-edited special issue for the last quarter of this year and welcome your suggestions for future special issues of the journal. This second issue starts with a paper entitled " An Approach to Solving the Surviv-able Capacitated Network Design Problem " where Sridhar and Park studied the problem of selecting links of a network to construct primary and secondary routes for transfer of commodity traffic between nodes of the network. Their technique allows the design of survivable and cost-effective networks. In the second paper, " Query Processing Strategies for Location-Dependent Information Services " , Jayaputera and Taniar propose a new approach to generate a query result for location-dependent information services (LDIS). They argue that choosing a square as the scope of a query and dividing it into four equal regions, where a user is a center point of the scope, results in a faster searching time to find targets queried and brings a bigger chance to get rare targets. In addition, by avoiding resubmitting the same queries when the query results missed, the approach reduced bandwidth use at both the server and client sides. The third paper, " Addressing SPAM E-Mail Using Hashcash " by Curran and Honan tackles a problem experienced by most of us. The authors present the Hashcash proof-of-work approach and investigate the feasibility of implementing a solution based on that mechanism along with what they called a " cocktail " of antispam measures designed to keep junk mail under control. Finally , in the last paper, entitled " MANET: Applications, Issues, and Challenges for the Future " , Dhar presents an informative survey of mobile ad hoc networks, describing the main characteristics of those networks and how they are being used, and discussing the most pressing issues and challenges associated with these temporary wireless networks. We hope that you enjoy this and the upcoming issues of IJBDCN. Our goal is to …

International Journal of Business Data Communications and Networking

Techniques for performing peer discovery to enable peer-to-peer (P2P) communication are disclosed. In an aspect, a proximity detection signal used for peer discovery may be generated based on one or more physical channels and/or signals used in a wireless network. In one design, a user equipment (UE) may generate a proximity detection signal occupying at least one resource block based on a SC-FDMA modulation technique. In another design, the UE may generate a proximity detection signal occupying at least one resource block based on an OFDMA modulation technique. The UE may generate SC-FDMA symbols or OFDMA symbols in different manners for different physical channels. In yet another design, the UE may generate a proximity detection signal including a primary synchronization signal and a secondary synchronization signal. For all designs, the UE may transmit the proximity detection signal to indicate its presence and to enable other UEs to detect the UE.

Transmission and reception of proximity detection signal for peer discovery

Providing reliable broadband wireless communications in high mobility environments, such as high-speed railway systems, remains one of the main challenges faced by the development of the next generation wireless systems. This paper provides a systematic review of high mobility communications. We first summarize a list of key challenges and opportunities in high mobility communication systems, then provide comprehensive reviews of techniques that can address these challenges and utilize the unique opportunities. The review covers a wide spectrum of communication operations, including the accurate modeling of high mobility channels, the transceiver structures that can exploit the properties of high mobility environments, the signal processing techniques that can harvest the benefits (e.g., Doppler diversity) and mitigate the impairments (e.g., carrier frequency offset, intercarrier interference, channel estimation errors) in high mobility systems, and the mobility management and network architectures that are designed specifically for high mobility systems. The survey focuses primarily on physical layer operations, which are affected the most by the mobile environment, with some additional discussions on higher layer operations, such as handover management and control-plane/user-plane decoupling, which are essential to high mobility operations. Future research directions on high mobility communications are summarized at the end of this paper.

A Survey on High Mobility Wireless Communications: Challenges, Opportunities and Solutions

A range of efficient wireless processes and enabling techniques are put under a magnifier glass in the quest for exploring different manifestations of correlated processes, where sub-Nyquist sampling may be invoked as an explicit benefit of having a sparse transform-domain representation. For example, wide-band next-generation systems require a high Nyquist-sampling rate, but the channel impulse response (CIR) will be very sparse at the high Nyquist frequency, given the low number of reflected propagation paths. This motivates the employment of compressive sensing based processing techniques for frugally exploiting both the limited radio resources and the network infrastructure as efficiently as possible. A diverse range of sophisticated compressed sampling techniques is surveyed, and we conclude with a variety of promising research ideas related to large-scale antenna arrays, non-orthogonal multiple access (NOMA), and ultra-dense network (UDN) solutions, just to name a few.

Compressive Sensing Techniques for Next-Generation Wireless Communications

This paper considers affine cyclic-prefixed block-based pilot-aided transmission (PAT) over the single-antenna doubly selective channel, where the channel is assumed to obey a complex-exponential basis expansion model. First, a tight lower bound on the mean-squared error (MSE) of pilot-aided channel estimates is derived, along with necessary and sufficient conditions on the pilot/data pattern that achieves this bound. From these conditions, novel minimum-MSE (MMSE) PAT schemes are proposed and upper/lower bounds on their ergodic achievable rates are derived. A pilot/data power allocation technique is also developed. A high-SNR asymptotic analysis of the ergodic achievable rate of affine MMSE-PAT is then performed which suggests that the channel's spreading parameters should be taken into account when choosing among affine MMSE-PAT schemes. Specifically, we establish that multicarrier MMSE-PAT achieves higher rates than single-carrier MMSE-PAT when the channel's delay-spread dominates its Doppler-spread, and vice versa.

Design and Analysis of MMSE Pilot-Aided Cyclic-Prefixed Block Transmissions for Doubly Selective Channels

Systems and methodologies are described that facilitate employing a scrambling code from a set of scrambling codes, which is indexed by primary synchronization codes (PSCs), to scramble or descramble a secondary synchronization code (SSC). The scrambling codes in the set can be designed to optimize peak-to-average power ratios and/or mitigate cross correlation. For example, the scrambling codes can be based on different M-sequences generated from disparate polynomials. In accordance with another example, the scrambling codes can be based on different cyclic shifts of the same M-sequence. According to another example, the scrambling codes can be based upon binary approximations of possible primary synchronization codes utilized in a wireless communication environment. Pursuant to a further example, the scrambling codes can be based on different Golay complementary sequences.

Scrambling codes for secondary synchronization codes in wireless communication systems

In a multi-user millimeter (mm) wave communication system, we consider the problem of estimating the channel response between the base station (BS) and each of the user equipments (UEs). We propose three different pilot training schemes/strategies, namely: 1) estimating mm wave channels separately at the UE’s; 2) joint estimation of mm wave channels of all the UE’s simultaneously at the BS; and 3) two stage process involving estimation at both the UE’s and the BS. We propose two random constructions for the pilot/training signals/beamforming weights and analytically characterize the mutual coherence parameter of the resulting sensing matrices for one of the constructions. By exploiting the structure in mm wave channels, we develop a generalized block orthogonal matching pursuit (G-BOMP) algorithm for channel estimation in all the three strategies. Furthermore, we establish sufficient conditions for exact support recovery by the proposed G-BOMP algorithm and derive an upper bound on the norm of the channel estimation error. We also study the performance of our G-BOMP algorithm in terms of the average beamforming gain and average spectral efficiency achieved via simulations. Our results show that the proposed G-BOMP algorithm outperforms the conventional OMP algorithm and other existing multiuser mm wave channel estimation techniques. G-BOMP also performs comparable to the computationally expensive compressive estimation using Newton ’s refinement technique, for the first pilot training strategy in which the UE’s estimate the channels separately.

Channel Estimation Strategies for Multi-User mm Wave Systems

We consider a cognitive radio system with M primary channels where users' data transmissions follow a slotted structure. We consider the scenario where the channel availability statistics are correlated across channels as well as across time slots. In each slot, the cognitive user (CU) senses channels one by one until a suitable channel is found for data transmission. CU adapts theCognitive Radio data rate based on the channel's fading gain. We employ a Markov chain model to capture the channel availability statistics across the slots. We address the problem of finding optimal sensing order/procedure in every slot based on the history of sensed channels (including the previous slots), in order to maximize the total CU throughput over N-slots. Using theory of optimal stopping, we derive recursive expressions for the optimal multi-slot CU throughput and find the optimal multi-slot sensing order/procedure using dynamic programming. We also study few sub-optimal sensing procedures. Using numerical results, we illustrate the gains in exploiting the correlation of channel availability statistics.

http://www.ee.iitm.ac.in/~arunpachai/papers/coml_cr.pdf

Throughput Optimal Multi-Slot Sensing Procedure for a Cognitive Radio

In previous work, we established necessary and sufficient conditions on pilot/data patterns that minimize the mean-squared error of pilot-aided channel estimates, given a pilot power constraint and a general linear time-varying channel model. Here we derive upper and lower bounds on the ergodic channel capacity of these MSE-optimal pilot-aided transmission (PAT) schemes. These bounds may be used to allocate power between pilot and data, as well as to choose among MSE-optimal pilot/data patterns. For example, the bounds show that frequency-domain PAT achieves higher capacity than time-domain PAT, or vice-versa, depending on the relative time- and frequency-dispersion of the channel.

/pdf/capacity-analysis-of-mmse-pilot-aided-transmission-for-2y5k75iefn.pdf

Arun Pachai Kannu

Papers

Design and Analysis of MMSE Pilot-Aided Cyclic-Prefixed Block Transmissions for Doubly Selective Channels

Scrambling codes for secondary synchronization codes in wireless communication systems

Channel Estimation Strategies for Multi-User mm Wave Systems

Throughput Optimal Multi-Slot Sensing Procedure for a Cognitive Radio

Capacity analysis of MMSE pilot-aided transmission for doubly selective channels