T. Aaron Gulliver

Classification of extremal double-circulant self-dual codes of lengths up to 62

A classification of all extremal double circulant self-dual codes of lengths up to 72 is known. In this paper, we give a classification of all extremal double circulant self-dual codes of lengths 74-88.

Graph coloring based spectrum allocation for femtocell downlink interference mitigation

Femtocell networks have great potential for mobile applications. However, interference due to the co-existence of macrocells and femtocells is a serious problem. In addition, dense femtocells introduce severe inter-system interference. In this paper, a graph theory based dynamic sub-band allocation technique is presented to avoid downlink interference. We model the cells and their mutual interference as graph elements, nodes and weighted edges, respectively. To maintain a tolerable interference level, the total bandwidth is divided into a number of sub-bands, and these are assigned to the femtocells using a graph coloring algorithm. The division is optimized to minimize the bandwidth used to meet user traffic requirements, and minimize the femto-to-macro interference. In addition, sub-bands are assigned to the femtocells to avoid inter-femto interference. An iterative spectrum management algorithm is also introduced.

Wireless Mesh Networks for In-Home IPTV Distribution

IPTV is considered to be the next killer application. A key, challenging issue is in-home IPTV distribution with affordable deployment cost and sufficient flexibility, scalability, and reliability. In this article, we first survey and compare the emerging wired and wireless communication technologies for broadband home networks, including transmission over power lines, phone lines, coaxial cables or Ethernet cables, and IEEE 802.1 In, ultra wideband and millimeter wave wireless technologies. Considering these promising candidates for future broadband home networks, we propose three wireless mesh network architectures. These enable consumers to enjoy anywhere, anytime IPTV services without rewiring their homes. We compare the cost, reliability, and scalability of the three architectures. We further study their admission regions for IPTV, that is, the number of IPTV connections that can be supported simultaneously with satisfactory QoS. Analytical and simulation results with H.264 HDTV sources over wired, single hop wireless, and multi-hop wireless paths are given. These results can provide important guidelines for future broadband home network design supporting IPTV services.

On self-dual codes over some prime fields

In this paper, we study self-dual codes over GF(p) where p = 11, 13, 17, 19, 23 and 29. A classification of such codes for small lengths is given. The largest minimum weights of these codes are investigated. Many maximum distance separable self-dual codes are constructed.

Classification of Extremal Double Circulant Self-Dual Codesof Lengths 64 to 72

Recently extremal double circulant self-dual codes have been classified for lengths n ≤ 62. In this paper, a complete classification of extremal double circulant self-dual codes of lengths 64 to 72 is presented. Almost all of the extremal double circulant singly-even codes given have weight enumerators for which extremal codes were not previously known to exist.

Differential amplitude pulse-position modulation for indoor wireless optical communications

We propose a novel differential amplitude pulse-position modulation (DAPPM) for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR). The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM depending on the number of amplitude levels and the maximum length of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about and more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM. When the number of bits per symbol is the same, PAM requires more power, and DH-PIM less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.

Performance Analysis of IPTV Traffic in Home Networks

A heterogeneous wired and wireless network architecture is proposed for in-home IPTV distribution. To identify the bottleneck in the home network and estimate the network capacity, we develop an analytical framework to quantify the maximum number of IPTV connections that can be supported with guaranteed QoS in the wired and multi-hop wireless networks, respectively. We extend the fluid flow model analysis to capture both the burstiness of IPTV sources and the time-varying characteristics of multi-hop wireless channels. Extensive NS-2 simulations with H.264 HDTV sources over wired and multi- hop wireless paths are given, which validate the analysis. The analytical and simulation results provide important guidelines for the planning of future home networks and IPTV systems.

New Good Rate (m-1)/pm Ternary and Quaternary Quasi-Cyclic Codes

Previous results have shown that the class of quasi-cyclic (QC) codes contains many good codes. In this paper, new rate (m - 1)/pm QC codes over GF(3) and GF(4) are presented. These codes have been constructed using integer linear programming and a heuristic combinatorial optimization algorithm based on a greedy local search. Most of these codes attain the maximum possible minimum distance for any linear code with the same parameters, i.e., they are optimal, and 58 improve the maximum known distances. The generator polynomials for these 58 codes are tabulated, and the minimum distances of rate (m - 1)/pm QC codes are given.

Joint Spatial and Temporal Spectrum Sharing for Demand Response Management in Cognitive Radio Enabled Smart Grid

Real-time demand response management (DRM) in smart grid (SG) requires a reliable wireless communication network with sufficient spectrum resources. However, the allocated spectrum for wireless communications is heavily under-utilized in the spatial and temporal dimensions. To solve the spectrum scarcity problem, cognitive radio (CR) and dynamic spectrum sharing have been proposed, but this can result in poor reliability. In this paper, the influence of wireless communication reliability on DRM is analyzed and the relationship between outage and DRM performance is derived. Outage results from not only interference and noise, but also the unavailability of spectrum resources. Therefore, joint spatial and temporal spectrum sharing is proposed to improve spectrum utilization. The SG network is divided into a Temporal Spectrum Sharing Region (TSSR) and a Free Spatial Spectrum Sharing Region (Free-SSSR). SG nodes in the TSSR can utilize the licensed spectrum when primary users (PUs) are idle, while in the Free-SSSR they can simultaneously share this spectrum with the PUs without using power control. Performance results are presented which show that joint spatial and temporal spectrum sharing can increase the SG spectrum utilization opportunities and lower the outage probability, which is beneficial for DRM performance.

MDS and self-dual codes over rings

In this paper we give the structure of constacyclic codes over formal power series and chain rings. We also present necessary and sufficient conditions on the existence of MDS codes over principal ideal rings. These results allow for the construction of infinite families of MDS self-dual codes over finite chain rings, formal power series and principal ideal rings.