Novel Applications of the UWB Technologies Part 7 pot

UWB Technology for WSN Applications 167 Due to the PN code having a higher rate than the information signal, there will be several chips representing a single information symbol. This adds redundancy to the signal and employs a processing gain due to the increase in the signal bandwidth. It facilitates to resist interference effects and enable secure communication in a hostile environment such that the transmitted signal cannot be easily detected or recognized by unwanted listeners. We consider single user, point-to-point UWB operation. But for multiple users, spread spectrum can be used as a multiple-access communication system where a number of independent users are required to share a common channel without an external synchronizing mechanism. Here DSSS technique is used prior with modulation, which greatly reduced the noise sensitivity (i.e. noise immunity). Spreading creates a lower power spectral density than the original signal; however the total transmitted power remains the same. This allows the SNR of the signal to be below the noise floor level. It has several advantages for the system, as the signal will be less likely to interfere with other users on the same spectrum. Also other unauthorized users are unable to detect the signal, as the signal amplitude will appear as a slight increase in noise, so adds security to the system. Modulation format: In this UWB system lower order modulation format is used for the transmission of sensor information. Table 4.2 shows the BPSK and PAM modulation format discussed by Haykin (2006). Polarity of data sequence b(t) at time t + - PSK PAM PSK PAM Polarity of PN sequence c(t) at time t +0 1  -1 -  -1 0 1 Table 4.2. BPSK and BPAM modulation format. Pulse shaping: The choice of the pulse is critical as its impulse response affects the PSD of the transmitted signal. Zeng (2005) has proposed several UWB pulse shapes where Gaussian pulse is more suitable for UWB transmission. To increase the derivative of the pulse, the relative bandwidth decreases while the center frequency increases for a fixed value of pulse width. The N th order Gaussian pulse can be generated by 2 (2 ) 10 (2 ) () f nn fe pt A ne      and Figure 4.5 shown different pulse shapes. We used Gaussian doublet (2nd order Gaussian pulse) because it is the most currently adopted pulse that meet the appropriate UWB operation with regulation explained by Benedetto and Giancola (2004), which is usually generated by the equation. 2 2 2 2 2 () (1 4 ) t p w t pt e pw     Here p(t) is a Gaussian pulse (Gaussian doublet) where pulse duration or width is much smaller than pulse repetition period, i.e. T p >>P w , so it can produce low duty cycle operation. Novel Applications of the UWB Technologies 168 Fig. 4.5. Gaussian pulse shape. The output of the modulator enters the pulse shaper filter, which acts as a low pass filter and after convolution operation between the modulated data and Gaussian pulse. Signal amplitude is shown for BPSK and BPAM in Figure 4.6 and transmitted pulse after shaping is shown in Figure 4.7. Fig. 4.6. Transmitted signal amplitude (BPSK & BPAM). UWB Technology for WSN Applications 169 Fig. 4.7. Transmitted pulse train after shaping. 4.3 Channel The UWB radio signal is ideally composed of a sequence of pulses that do not overlap in time. Each pulse is confined within a specific time interval and the pulse itself has finite duration. The received signal can be expressed as r(t) = s(t)+n(t), 0  t  T. where n(t) denotes a sample function of the additive white Gaussian noise (AWGN) process with power spectral density of N o /2 W/Hz. Here single user point-to-point communication system is considered with the absence of inter symbol interference (ISI) and multi-user interference (MUI) phenomenon. Figures 4.8 and 4.9 show the channel output of BPSK and BPAM respectively. Fig. 4.8. AWGN channel output (BPSK), where Eb/No=5 dB. Fig. 4.9. AWGN channel output (BPAM), where Eb/No=5 dB. Novel Applications of the UWB Technologies 170 The BPSK output shown in Figure 4.8 is more noise like and undetectable comparing to BPAM output shown in Figure 4.9. The probability of error depends on the modulation scheme and Signal to Noise Ratio (SNR). The performance of the impulse radio signal over the AWGN channel can be realized with the BER performances as shown in Figure 4.10 and 4.11, where number of pulse per bit is one and four, while different modulation technique is used. In the DS-UWB propagation through AWGN channel, transmitted pulses are delayed and attenuated due to thermal noise, but multi path effect, ISI and MUI were not considered. Here by increasing the number of pulses per bit ( N s ), the received energy is increased by a factor N s , without increasing the average transmitted power (P av ). To increasing the number of pulses per bit we can achieve better SNR performance. Fig. 4.10. BER performance BPSK, BPAM, DPSK, BPPM ( Ns=1, 4). UWB Technology for WSN Applications 171 Fig. 4.11. BER performance BPSK, BPAM ( Ns=4). 4.4 Receiver At the receiver shown in Figure 4.3, de-modulation operation is performed with the noisy signal. The constellation diagram is shown in Figure 4.12 and the signal after demodulation is shown in Figure 4.13. The received signal is successfully recovered by using an energy detection method. A sample of matlab code for detection is shown in Figure 4.14. Fig. 4.12. Received signal constellation (BPSK, Eb/No=2, 5) Fig. 4.13. Received signal amplitude after demodulation. Novel Applications of the UWB Technologies 172 The decision is obtained by applying a simple majority criterion. Given the number of pulses falling over a threshold and comparing this number with the number of pulses falling below the same threshold, the estimated bit corresponds to the higher of these two numbers. An error occurs if more than half of the pulses are misinterpreted. So this decision factor achieves accurate reception and by increasing the number of pulses per bit provides more efficiency. The length of PN code ( f_chip ) is used to correlate with the received bits after demodulation while f_chip/2 decision metrics provides the estimated repeat bits at the receiver shown in Figure 4.15. Finally N s /2 decision threshold facilitates to recover bits in the de-repetition process, which are compared to the transmitted bits for error estimation. For large number of transmitted data, no error is found as shown successfully by the simulation results. Fig. 4.14. Detection code. Fig. 4.15. Output after detection ( 10110010), Ns = 4. The proposed transceiver model is efficient and ensures reliable transmission, so it is suitable for sensor network communication system. Here, by increasing the number of pulses per bit ( Ns), the received energy is increased by a factor Ns, without increasing the average transmitted power but at the same time compensating the bit rate of dividing by Ns. Data is successfully recovered by energy detection technique (detect and avoid), which facilitates the design simplicity at the receiver by avoiding pulse synchronization and coherent detection. Moreover having 50% of data corruption during the propagation, the system still recovers the bit stream accurately (Ns/2, bit=8, Tx bit=8 4, Sum> Ns/2)  . Also UWB Technology for WSN Applications 173 power emission and consumption are very low .(Power = 794 W and Energy per pulse = 280 nW).So it’s a noise like signal, which is difficult to detect by unwanted user and immune to interference with other existing radio operating in the same band. 5. Summary UWB technology is feasible for the implementation of sensor networks as it offers high robustness to interference and provides low complexity receivers and transmitters with low energy consumption. The IEEE 802.15.4a standard enables UWB-based sensor networks, which offer a high degree of flexibility and includes modulation, coding, and multiple access schemes that permit non-coherent receiver design. The specification for UWB LR- WPAN devices incorporates a number of optional enhancements to potentially improve performance, reduce power consumption and enhance coexistence characteristics. In particular, DS-UWB is a suitable communication platform for wireless sensor networks where accuracy and reliability is more important factor than bandwidth utilization. Due to the ability of noise immunity and low probability of detection and interference rejection, DS- UWB is a good choice for wireless sensor networks. Pictorial signal behavior shown in the simulation process helps to realize the above-mentioned facts. The UWB information rates as a function of transmission distance over AWGN and other channels can be considered for further development. Moreover, in future, multiple access interference on transceiver design can be investigated in a multi user environment. It might be interesting to explore the coding-spreading tradeoffs, channel estimation and design of optimum transceiver architecture. 6. References Allen, B. (2004). Ultra wideband wireless sensor networks. IEE Seminar on Ultra Wideband Communications Technologies and System Design, King’s College, London. Pp: 35- 36 Azim M A, et al., (2008). Direct Sequence Ultra Wideband System Design for Wireless Sensor Network. Proceedings of the International Conference on Computer and Communication Engineering (ICCCE'08). Kuala Lumpur, Malaysia. Pp: 1136 to 1140 Azim M A, et al., (2008). Development of Low-cost Sensor Interface for Wireless Sensor Network Monitoring Application. 5th International Conference on Information Technology and Applications (ICITA 2008), 23 - 26 June 2008, Cairns, Queensland, AUSTRALIA. Benedetto, M. D. and Giancola, G. (2004). Understanding ultra wide band radio fundamentals. Prentice Hall. Communications Engineering and Emerging Technologies Series. Pp: 121-234 Haykin, S. (2006). Digital communications. John Wiley & Sons, Inc. New York, NY, USA. Page 445 to 471 IEEE802.15.4 specifications. (2003). Online article, Retrieved June 22, 2006, from http://www.ieee802.org/15/pub/TG4.html IEEE 802.15.4a. (2007). IEEE Standard for PART 15.4: Wireless MAC and PHY Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs): Amendment 1: Add Alternate PHY. Retrieved July 2, 2007, from Novel Applications of the UWB Technologies 174 http://standards.ieee.org/getieee802/download/802.15.4a-2007.pdf Oppermann, I., Hamalainen, M., and Iinatti, J. (2004). UWB theory and applications. Wiley Press. Reed, J. H. (2005). An introduction to Ultra wideband communication systems. Prentice Hall. Zeng, D. (2005). Pulse Shaping Filter Design and Interference Analysis in UWB Communication Systems. Dissertation Submitted to the Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University. Zhang J, et al (2009). UWB Systems for Wireless Sensor Networks. Research article by Mitsubishi Electric Research Laboratories. Available online at http://www.merl.com 9 Green Femtocell Based on UWB Technologies Moshe Ran 1 and Yossef Ben Ezra 2 1 MostlyTek Ltd. 58 Keshet St., Reut 2 H.I.T - Holon Institute of Technology, Holon, Israel 1. Introduction The rapid evolution of mobile communications through four generations of mobile communication, envisages the operation at 100Mb/s for mobile users and at 1Gb/s for stationary applications in the near future. The tremendous increase of data rates must be considered in the context of four decades of the mobile cellular technologies progress since its first introduction by the Nippon Telephone and Telegraph Company (NTT) in the late 70's Rappaport (2002). On the other hand, fixed wireless communications are already available to provide over 300 Mbps raw data rates through wireless local area networks (LAN) protocols as 802.11n, and over 1Gbps through Ultra Wideband (UWB) in wireless personal area networks (PAN), see (ECMA-368), (ECMA-387). With the introduction of the femtocell concept Zhang (2010), new opportunities have been opened for approaching the 4G mobile vision through fixed mobile convergence (FMC). Femtocell Access Point (FAP), are low power access points that connect mobile terminal to the mobile core network using wired broadband or fixed broadband wireless technologies. The FAP provides viable opportunities for mobile operators, to meet the indoor coverage challenges for most demanding applications at low cost. We propose a novel concept of 4G femtocell, denoted a "Green Femtocell", and high level network architecture to support the new paradigm of FMC, in which convergence of 4G cellular with short-range wireless and wired are realized. The proposed approach paves the way of green framework in which increase by x100 in energy efficiency and x100 reduction of human exposure to wireless radiation become feasible. Our approach relies on radio-over-fiber and all-optical solutions that can already be considered "green" in offering reduced energy consumption to alternative wireless access solutions, see CELTIC Purple Book (2011). The new concept is based on the following novel technical and business entities (Fig. 1):  We introduce a green remote Home Access Node (HAN) that relays range of radio protocols, including UWB, WLAN, LTE-A, and IEEE 802.16m as radio signals over hybrid wireless-fiber media from 1.8 GHz to 10.6 GHz; with strict limitation of radiated power. Wireless radiation for indoor environments is reduced by 2-3 order of magnitudes, while potentially support target 1Gbps end-user data rates, by using dual-mode cellular-UWB for most common indoor applications. Indoor HAN should support mobile users at distances ranging from 0.3m to 30m over-the-air. For outdoor Novel Applications of the UWB Technologies 176 and longer range indoor topologies, we enable protocol-transparent architectures capable of relaying range of radio protocols from 30 to 300 m.  Processing for multiple HANs is centralized with optical Multi-cell Base Station (O- McBS) capable of performing parallel multiple input multiple output (MIMO) processing of radio-over-fiber (ROF) links over 100's of GRANs. Unlike the McBS approaches suggested in Foshini (2006) and Gambini (2010), our O-McBS approach involved with optical MIMO over multi mode fiber (MMF). The multicell processing performed at McBS enables clear benefits of centralized approach to interference management over the hybrid wireless-fiber medium and efficient radio resource managements (RRM). We note that MIMO over MMF is a very recent enabling technology that has been shown to attain 400Gb/s signalling rate over several hundreds of meters of MMF at 10 -10 BER Greenberg (2007). A promising solution for radio signalling and multiple access over hybrid wireless-MMF is based on orthogonal frequency-division multiple access (OFDMA). However, most of the works have addressed only the indoor wireless channels Perez (2009).  O-McBS are connected through optical femto gate way (O-FemtoGW) to core network through Tb/s optical links. O-FemtoGW multiplex data from 10's of O-McBS, and forms through all-optical real-time processing an optical OFDM (O-OFDM) signal carrying 100Gb/s. Recently, works on all optical FFT schemes to implement efficiently O-OFDM to enable 1 Tb/s have been published by Hillerkuss (2010). Recent survey on O-OFDM with MIMO can be found in Shieh (2010), and general aspects of O-OFDM in Armstrong (2009) and Gidding (2009). R F E/ O O/E PHY PHY HAN #1 PHY O- McBS HAN #n Mult i Mode F iber ( MMF ) Femto - N SP AAA Network mng . MM F MM F 1 Tb s/s NSP: Network service provider MMF: Multimode Fiber O-McBS: optical multicell BS RRM: radio resource management MAC: Medium access control E/O: Electrical/Optical converter O/E: Optical/Electrical converter Fig. 1. Green Femtocell Access Network (high-level architecture). [...]... for the direct E/O conversion of the W-CDMA signal into radioover-fiber (ROF) signal The ROF UMTS signal propagated through a standard MMF (type OM3) of the length of 30m, and was detected by a PIN diode Then, the detected signal was onward transmitted through the tested channel to the W-CDMA receiver The purpose of this experiment was the study of the wired channel performance The measured gain of the. .. symbols maximum achievable diversity order of KLNT N R can be achieved, where L is the number of resolvable paths 192 Novel Applications of the UWB Technologies  Beam forming for MB OFDM UWB is presented in Malik (2006) It is shown that the signal bandwidth has little impact on beam width or direction The high level scenario of MB-OFDM UWB with MIMO processing over the wireless channel is shown in Fig...Green Femtocell Based on UWB Technologies 177 The proposed architecture leverages and extends the concepts and technologies of UWB radio over optical fiber (UROOF) Ran (2010a, b), Ben-Ezra (2010), and further investigated in the context of future mobile technologies in Ran (2009) and Altman (2010) Our technical approach is directed to solve the crucial problem of interference management in local... channel is about 15dB Although the combined wireless-wired channel causes the degradation of EVM in the range of 8% -15%, still the satisfactory performance of EVM values below 11% is observed Fig 9 EVM and link gain for the wireless-wired case The HAN is wirelessly connected to BS and connected to the user through VLR-DAS optical segment 188 Novel Applications of the UWB Technologies 4 4G green femtocell:... aimed to simplify and reduce the cost of the HAN implementation In this example, HAN#1 serves as the Master Unit (MU) that communicates with the HBS (or external macro BS either directly, or through a repeater) over the air to simplify the installation of the home network The other HAN's transmit the radio signals over the air to the target UE Case 2: Enterprise "Green Hospital" The Green Hospital represents... use of nearby indoor femtocells and thus clearly improve the overall capacity of the network From interference point of view, 178 Novel Applications of the UWB Technologies open access is superior to closed access, since it allows customers to connect to nearest access point Thus it enables reducing the overall use of system resources (power-frequencytime) Possible drawback to this approach is the. .. networks, there is an inherent inconsistency between the wish for mobility of the monitored patients and the interference of the radio signals with the sensitive diagnostic equipment At present, some 8-10 functions per patient are wirelessly recorded The number of monitored functions will grow rapidly in 185 Green Femtocell Based on UWB Technologies the coming years In many cases the monitoring of patient... www.ict-freedom.eu) aims at improving the efficiency of networks with massive femtocell deployment The focus is on addressing the key question: How much the whole system efficiency can be improved by exploiting the available quality of the IP-based backhaul link? 179 Green Femtocell Based on UWB Technologies The solutions addressed in FREEDOM include the two main flavours of the 4G femtocell paradigm, namely... problem The performance of CAS depends very much on the degree of cooperation In one extreme, the CAS consists of several distributed antennas which are connected to a central processing unit This type of CAS is the DAS case, which has the best performance In the other 183 Green Femtocell Based on UWB Technologies extreme, the BTS only exchange limited information, normally in order to boost the performance...   xOFDM , k (t  kTOFDM )exp  j 2 f( k mod 6)t       k 0  Where, xOFDM , k (t ) is kth the OFDM symbol of duration TOFDM , N is the number of transmitted OFDM symbols and f k is the carrier frequency over which the symbol is transmitted The designed value for TOFDM is 312.5ns, where information length is 242.4ns, 9.5ns kept for guard time, and 60.6ns are length of the cyclic prefix, providing . making use of nearby indoor femtocells and thus clearly improve the overall capacity of the network. From interference point of view, Novel Applications of the UWB Technologies 178 open. on UWB Technologies 177 The proposed architecture leverages and extends the concepts and technologies of UWB radio over optical fiber (UROOF) Ran (2010a, b), Ben-Ezra (2010), and further. Novel Applications of the UWB Technologies 174 http://standards.ieee.org/getieee802/download/802.15.4a-20 07. pdf Oppermann, I., Hamalainen, M., and Iinatti, J. (2004). UWB theory and applications.