WiFi network for long distances applications

The needs for bridging of digital divide in the rural communities and the economics of currently available broadband access technologies have motivated us for innovation and deployment of the new system designs and applications. The widely available and flexible WiFi technique meets the cost and suitability targets for the rural broadband applications. To cope with the special requirements of rural communication. amendments of 802.11 standards at the MAC protocol level has been introduced. These amendments are important due to the shortcomings of WiFi over long distances under the power constraints. This chapter proposes a new 802.11 point-to-multipoint (PMP) technique based on TDD/TDMA technique by using one of the access points in the system as centralized/gateway point to the other APs. The discussion includes the TDMA design and, architecture on top of the conventional 802.11 MAC. The protocol convergence at the gateway between the access network and the backhaul is also presented. The simulation results present the performance analysis and validate the efficiency of the proposed schem

Interference in femtocell network

Femtocell network is a new technology that uses the advantage of an Internet backbone to enhance the cellular coverage in residential or small business areas. However, due to the expected random deployment of the femtocell access point (FAPs), there is a strong probability of interference among the femtocell nodes and between the femtocells and the macrocell nodes. In this chapter, an interference enhancement for multi-femtocells is developed and designed for two tiers macro-femtocell networks. An adaptive power control is calculated based on selecting the minimum interference channel with the optimized channel gain. In the simulation a number of the FAPs, the distance between the macrocell and the femtocell and the path loss between the macrocell node and the FAPs are used as design parameters. The results show a performance enhancement in the interference degradation rati

Road side-to-vehicle communications

Wireless vehicular communication (WVC) has been identified as a key technology for intelligent transportation systems (ITS) for the past few years. IEEE 802.1 " 'Iproposed standard for the physical and MAC layer of the WVC devices. The main objective of the standard is to change the frame format in order to increase the delay spread tolerance introduced by the vehicle mobility, in which the channel bandwidth is scaled from 20 MHz. i.e.. 802.11 a to 10 MHz, i.e., 802.11 p. This chapter proposes the TD~·lA technique with fixed time slots and a guard band between the slots to ensure interoperability between the wireless devices to communicate in rapidly changing environment where transactions must be completed in small timcframes. The new TDMA sub-layer is proposed to be on top of the coventional 802.llp CSMA/CA MAC. We have found that 802.11 p-based TDMA can achieve much higher throughput compared with the conventional 802.11 p-based CSMA/CA, as the distance, vehicle speed and numbers increase. Ns-2 simulation results present the performce analysis and validate the efficiency of the proposed schem

Performance Enhancement Of Ultra-Wideband Power Control Using Ranging And Narrowband Interference Mitigation

Power control is a critical parameter for the design and evaluation of ultra-wideband (UWB) based ad-hoc networks due to its distributed control nature and non-fixed topology. Since the ad-hoc networks are infrastructure-less only local information is available for each node to maintain the limited resources available in the network. In UWB indoor networks the main issues in power control are the channel gain fluctuations induced by dense multipath and interference arising from the narrowband systems. In this thesis we have introduced a joint UWB physical/ medium access control layer (PHY/MAC) design for direct-sequence-based UWB (DS-UWB) power control design by exploiting the high time resolution of the UWB signal for channel gain improvement and mitigates the narrowband interference to reduce bit error rate (BER) and so enhance the throughput.The fine time resolution of UWB signals enables high ranging estimation resolution, which leads to more accurate transmitted power control. However, in dense multipath fading an accurate ranging is a problematic due to non-line-of-sight (NLOS) propagation environments. In this thesis we propose a maximum likelihood algorithm enhanced with synchronization scheme to estimate the time delay of direct-path signal in NLOS multi-path fading environment and mean acquisition time. The algorithm is examined under various doublet Gaussian pulse widths and bit energy-noise ratio )(pT)(0NEb and gives lower ranging error (0.32m) compared to others (eg. CRLB is 0.84m). The closer the narrowband interference band to the centre frequency of the UWB signal, the more signal-to-interference-noise ratio degrades. In this thesis we discussed a mitigation approach by using the flexibility of the doublet Gaussian pulse generation, where a notched band is contributed in the pulse spectrum to avoid the narrowband interferer frequencies. In this case worldwide interoperability for microwave access (WIMAX) and wireless local area network (WLAN) are used. The results are compared with orthogonal frequency division multiplexing-based UWB (OFDM-UWB) before and after mitigation. It was observed that DS-UWB shows better performance after pulse adaptation (1dB better than cognospectrum). The performance of power control using the proposed ranging and pulse adaptation schemes is investigated for different number of nodes. It is seen that, bit error rate of 10-4 can be achieved for 20 users maintaining 14.2dB SINR. Also the same bit error rate can be achieved for bit error rate for SINR using 40 pulses per bit (). The results have been indicated that the proposed approach is able to achieve better BER (1.6 dB) and throughput (12% more for 40 users) than previous related research works. dB3.12s

Femtocell network : challenges and future trends

Currently, Femtocell technology emerged for cellular wireless networks, which has rapidly engrossed cellular industry. The principle of femtocell to mobile operators is to reduce the network operation cost and increase indoor coverage which is also considered a possible path to the fixed-mobile convergence (FMC) goal. Femtocell access point (FAP) or home base station (HBS) is a base station designed for use in user premises (home or small business). It intends to serve small number of users i.e. 4 users and covers about 30 meter square similar to existing WiFi access points. The uniqueness of femtocell in contrast with micro and macrocellular it connects to cellular network through broadband network i.e. xDSL. The motivation of femtocell is to improve signal quality in indoor environments and provide high speed wireless access mobile-Internet users. However, femtocell introduces new challenges to the mobile operators (MOs) in terms of handoff between femto and macrocells, interference management, localization and synchronization, security and network management. Accordingly, the objective of this chapter is to studies the challenges and future trends for femtocell communication, and summarize by explored some open issues as wel

Real-Time personalized stress detection from physiological signals

This is the era of modern life. The era of email, text messages, Facebook and Twitter, careers Crisis news coming from everywhere at any time. We (human) are assaulted with facts, pseudo facts, jibber-jabber, and rumour all posing as information. We text while we’re walking across the street, catch up on email while standing in a queue. When people think they’re multitasking, they’re actually just switching from one task to another very rapidly. It has been found to increase the production of the stress that results overstimulate brains and cause mental fog or scrambled thinking. However, stress management should start far before the stress start causing illnesses. In this paper, a real-time personalized stress detection system from physiological signals is introduced. It is based on Pulse rate and temperature. That could record a person’s stress levels

Lightweight TDMA Protocol for wireless vehicular communications

Wireless vehicular communications (WVC) has been identified as a key technology for intelligent transportation systems (ITS) for a few years ago. IEEE 802.11p (WAVE: wireless access in vehicular environments) is the proposed standard for physical and MAC layer of WVC devices. The standard is extended from 802.11 protocols. The main objectives of the standard are to change the frame format and increase delay spread tolerance introduced by vehicle mobility, in which the channel bandwidth is scaled from 20 MHz in 802.11a to 10 MHz in 802.11p. However, to ensure interoperability between vehicles communicate in rapidly changing environment where a packet transmission should be completed in short time-frame is a problematic issue. This poster proposes WiFi-based TDMA technique with flexible time slots and guard bands to tackle this problem. The new TDMA sublayer is compatible with the 802.11p standard to ensure the feasibility of adoption by any vendor. The simulation results present the performance analysis and validate the efficiency of the proposed method