Mohammad Tamim Alkhodary Ali Al- Saihati

1. King Fahd University of Petroleum & Minerals Electrical Engineering DepartmentEE 578 Simulation of Wireless SystemsIEEE 802.15.4a UWB System Model Mohammad TamimAlkhodary Ali Al-Saihati

2. Outlines • IEEE 802.15.4a Introduction. • IEEE 802.15.4a History. • Sensor Network Requirements. • IEEE 802.15.4a UWB System Specifications. • IEEE 802.15.4a Coding • References

3. IEEE 802.15.4a Introduction • In the mid 90’s, UWB was introduced in wireless communications. • Nowadays, UWB has been adopted in low power low range wireless networks. • Example: sensor network • It has a low complexity, mandates to consume low power, mitigates (resists) multipath fading, avoids interference caused from the environment or between devices and allows precise ranging among the devices in the network. • This led to establish the IEEE 802.15.4a standards.

4. IEEE 802.15.4a History • The creation of IEEE 802.15.4a was begun in November 2002 interest group ‘a’ to find an alternative physical layer for the IEEE 802.15.4 Wireless Personal Area Network (WPAN) standard. • By March 2003, Task Group (TG4a) was officially formed aiming to create 802.15.4a standards. • The specifications of the baseline were approved in March 2005. • Two optional technologies were presented in the baseline: UWB Impulse Radio (IR) and Chirp Spread Spectrum (CSS). • The IEEE-SA Standards Board approved the protocol and then it was published in June 2007.

5. Sensor Network Requirements • Used to monitor or control a process in a field such as monitoring the temperature of the environment. • To make the sensing process effective, certain requirements are needed. • Cost of the sensor device must be low so that it accommodates a large number of sensor devices. • The transceivers should be suitable for any the place it will work in it and small. • The sensor must conserve battery power for several years without dying. • The transfer of data must be reliable.

6. IEEE 802.15.4a UWB System Specifications • The IEEE802.15.4a protocol supports different operationsand parameters. • Ability to turn on or off the radio transceiver within the network. • Determine the energy of the received signal. • Characterizing the quality of the received signal passed through the link. • Performs Clear Channel Assessment (CCA) which indicates weather the medium is idle or busy. • Performs channel frequency selection. • Precise ranging is used in UWB IR only.

7. UWB devices could work in three frequency bands: sub-gigahertz band (250–750 MHz), low band (3.1–5 GHz) and high band (6–10.6 GHz). • The UWB frame is composed of three major components: the SHR preamble, the physical layer header (PHR) and the Physical layer Service Data Unit (PSDU). • The UWB emission limit is – 41.3 dBm/MHz found by calculating the emission of power spectral density (PSD). • The power transmitted is more than 37 mW and 96.3 mW respectively for the bandwidths 500 MHz and 1354 MHz.

10. Multiple Access Scheme (MCM) • The multiple access scheme (MCM) must be able to detect the received signal coherently and non-coherently. • This by applying the waveform for the hybrid modulation:

11. Time hopping for 802.15.4a

12. Start of Frame Delimiter (SFD) • Start of frame delimiter (SFD)is inserted for the packet to indicate the end of the preamble. • The SFD detection results in accurate frame synchronization and ranging. • Two types of SFD: long and short SFD. • Short SFD has 8 preamble symbols with polarity of 0, 1, or -1 for each symbol. • Long SFD has 64 preamble symbols. • The SFD processing gain is higher than the individual preamble symbol by a 6 dB.

13. SFD in the 802.15.4a frame

14. IEEE 802.15.4a Coding • Coherent detection is used to achieve high coding rate. • The systematic bits are used to determine the PPM position of the burst and are visible to both noncoherent and coherent receivers. • The parity bits are modulated on the burst phase which is visible only to coherent receivers.

15. RS and Convolution Codes • Convolutional code generator functions: g1= [010] , g2= [101] • Systematic (51,43,8) Reed–Solomon code is used . • This coding scheme allows to have different decoding schemes depending on the complexity and performance. • No decoding: since the RS code is systematic, the receiver can just ignore the redundant bits of the RS code as well as the systematic convolutional code and decode the information bit by bit. • Hard decoding of the RS code: using standard decoding of RS codes, the receiver can decode the signal without using the redundant information of the convolutional code. • Hard decoding of convolutional code followed by hard decoding of RS code. • Soft decoding of convolutional code followed by decoding of RS code. • Turbo-decoding: exchange of soft information between convolutional code and RS code.

16. IEEE 802.15.4a coding scheme for hybrid modulation

17. Thank You

18. References [1] Ben Slimane, J. Song, Y and Kouba, A. “A Three-Tiered Architecture for Large-Scale Wireless Hospital Sensor Networks”. Workshop Mobi Health Info 2009 in conjunction with BIOSTEC 2009. 24 Nov, 2009. [2] Kinney,P and Zhang. “UWB Systems for Wireless Sensor Networks”. Proceedings of the IEEE. Vol. 97, No. 2. Feb 2009. [3] Socorro, R and Heras, J. “Embedded Systems for energy efficient building”. eDIANA. 29 May, 2009.