Motivated by a scheduling problem that arises in the study of optical networks we prove the following result, which is a variation of a conjecture of Haxell, Wilfong and Winkler. Let k, n be two integers, let wsj , 1 ≤ s ≤ n, 1 ≤ j ≤ k be non-negative reals satisfying ∑k j=1 wsj < 1/n for every 1 ≤ s ≤ n and let dsj be arbitrary non-negative reals. Then there are real numbers x1, x2, . . . , xn...

Nowadays, cognitive radio is one of the most promising paradigms in the arena of wireless communications, as it aims at the proficient use of radio resources. Proper utilization of the radio spectrum requires dynamic spectrum accessing. To this end, spectrum sensing is undoubtedly necessary. In this chapter, various approaches for dynamic spectrum access scheme are presented, together with a su...

For video transmissions using MPEG compression there is a clear trade-off between picture quality, encoding latency and jitter. Interactive applications that are dependent on high quality as well as low latency cannot fall back on compressed video, but must rely on fully uncompressed video transmissions. Since the high bit rates of such transmissions consume bandwidths between 300 Megabit/s and...

Live streaming media applications are becoming more popular each day. Indeed, some important TV channels already broadcast their live content on the Internet. In such scenario, Peer-to-Peer (P2P) applications are very attractive as platforms to distribute live content to large client populations at low costs. A thorough understanding of how clients of such applications typically behave, particu...

Information theoretical analysis has shown that the application of multiple antennas at both sides of the wireless communication link can greatly improve the capacity/throughput. Although many mathematical analyses are performed on such a system, generally referred to as a MultipleInput Multiple-Output (MIMO) system, a physical interpretation of the MIMO principle is still lacking in literature...

[3] S. Adireddy and L. Tong, " Optimal placement of known symbols for slowly varying frequency selective channels, " accepted to IEEE Trans. Wireless Communications, 2003. Optimal placement of known symbols for frequency-selective block-fading channels, " IEEE Trans. [7] B. Hassibi and B. Hochwald, " How much training is needed in multiple-antenna wireless links, "

In wireless networks, devices (or nodes) often have a limited battery supply to use for the sending and reception of transmissions. By allowing nodes to relay messages for other nodes, the distance that needs to be bridged can be reduced, thus limiting the energy needed for a transmission. However, the number of transmissions a node needs to perform increases, costing more energy. Defining the ...

The area capacity scaling of Wi-Fi has been thought to be poor due to the 802.11 MAC enforcing single transmissions in overlapped cell coverage areas. This is based on the assumption that the energy detection and virtual carrier sense MAC mechanisms at every station correctly detect ongoing transmissions and thus prevent new transmissions. However overlapped or faded packet headers can cause st...

In this article, we look into how the LTE network can efficiently evolve to cater for new data services by utilizing direct communications between mobile devices and extending the direct transmissions to the unlicensed bands, i.e., device-to-device (D2D) communications in conjunction with LTE-Unlicensed. In doing so, it provides an opportunity to solve the main challenge of mutual interference ...