Recent Advances in Communications and Networking Technology (Formerly Recent Patents on Telecommunication) (Discontinued) - Volume 3, Issue 2, 2014

Accuracy and scalability contribute to the quality of location solutions in wireless networks. While accuracy is a parameter addressed in all location technologies, scalability is often relegated. However, scalability becomes an actual issue in positioning solutions based message exchange (e.g. measuring ranges from beacons). The passive TDOA algorithm is a solution designed to localize terminals in a mobile ad hoc network in a passive way. It is achieved by computing time-differences of arrival from messages being exchanged by other network nodes (i.e. the active nodes), but just listening to the radio channel. In advanced stages of the passive TDOA algorithm (i.e. autonomous passive TDOA recently patented), it is able to compute the position of the unknown node (i.e. the passive node) and of the nodes which the listened location messages belong to (i.e. the active nodes). Thus, the requirement of active nodes informing about its own position to passive nodes is fulfilled. From the network perspective, the impact of this joint-position computation: it boosts the scalability since less information is transmitted and it helps to improve the accuracy of the active nodes, because passive nodes can report several positions regarding a single active node. However, the accuracy of the positions computed by means of the passive TDOA algorithm needs to be good enough to attend the user’s demands. The aim of this work is analyzing the accuracy achieved by the passive TDOA, focusing on the loss of precision due to passivity if compared with conventional two-way time-of-arrival active solutions, which passive TDOA is rely on.

Currently all-optical Dense Wavelength Division Multiplexing (DWDM) communication networks [1] are able to transport packet data end-to-end without the need to convert the transport wavelength(s) to an electrical signal. These networks today operate similar to their electrically-based network counterparts. That is, while all-optical DWDM networks have distinct advantages over electrically-based transport networks [2, 3], they have inherited much of their operational methodologies from previous electrically-based technologies. This paper discusses all-optical DWDM hardware technologies [4, 5] combined with newly developed algorithms [6] for network device addressing, and optical path construction; in a manner that creates an all-optical network topology called Application Lambda Switching. This new networking topology does not limit bandwidth, eliminates congestion, and Quality of Service (QoS) [7] issues. It can diagnose outages, faults, detect expansion, device failures, track inventory, and map itself all in real-time without the need for additional add-on technologies, or protocols typically used to perform these functions [8-10]. Application Lambda Switching (AλS) algorithms allow network access devices, not core-networking devices, to determine the bandwidth/speed of connections. AλS also utilizes an addressing algorithm that calculates device hardware addresses; therefore, the optical infrastructure itself can track its own topology and activity through the exchange and re-calculation of device addresses.

Alamouti proposed orthogonal STBCS for two transmit antennas with code rate one. Tarkoh investigated for three to eight transmit antennas with code rate 1/2. Jafarkhni proposed for non orthogonal STBCS four transmit antennas with code rate one. The theory of space-time block codes was further developed by Weifen Su and Xian-Gen Xia. They defined space time block codes in terms of orthogonal code matrices. The properties of these matrices ensure code rate of 7/11 and 3/5 for 5 and 6 transmit antennas. For five, six, seven and eight transmit antennas, four generalized complex orthogonal space-time block codes of code rate with 2/3, 2/3,5/8, and 5/8 proposed recently . This paper intends new matrix GCOD Space time block codes for five, six, seven transmit antennas which can send 8 information symbols in a block of 8 channels with code rate of 1.

In the advanced communication system multi carrier and multichannel technique is used. Due to the physical properties of the channel some undesirable effects occur on the transmitted signals. At the receiving end, signals get attenuated, distorted, delayed, and phase shifted. In order to compensate for these effects perfect and up-to-date channel estimation is needed. In this paper, we have proposed modified step size leaky least mean square (MSS-LLMS) channel estimation technique for MIMO-OFDM system. The BER performance of the proposed scheme is compared for AWGN, Rayleigh, Rician and Nakagami-m fading channel. The bit error rate of the proposed method is reduced to 10-24 for the signal to noise ratio of 1 to 35.The proposed scheme is less complex that the RLS.

Location management is an important part in mobile cellular networks since the registered devices can change location while connected to the network. Location management has been of prime research interest over the past decades and several mechanisms have been proposed for legacy systems. However, these mechanisms have to be revisited in the scope of LTE and especially 5G networks where new usage scenarios emerge. In this paper we examine the suitability of existing solutions for 5G networks. Towards this goal we provide a summary of the existing proposals and also analyze a number of patents to verify what the industry believes as really feasible solutions. Then we pinpoint the problems to be expected in 5G networks, with respect to location management, and we propose a future proof path for the design of new location management schemes.

Internet service providers (ISP) are offering 4G network services through several wireless technologies such as WLAN, WiFi, WiMAX, LTE, etc. Thus, multimode devices will be able to manage communication links with different networks and support seamless mobility in these networks. To make decision for network selection during handoff, this paper proposes an Agent based vertical handoff decision algorithm that motivates users to periodically obtain the decision parameters and to identify optimal cost for decision function. The proposed handoff decision scheme uses agent technology. Link Monitoring Agent (LMA) is used to identify the decision parameter. The Handoff decisionmaking agent evaluates the decision function. These agents interact with each other in order to accelerate the handoff decision operation during vertical handoff.