SDR and UWB By : Ahmad Bakhtafrouz

What is UWB? FCC Definitions UWB Signaling - Impulse Radio UWB Advantages Modulation Types UWB Challenges UWB Applications - Single-carrier-based Modulation Multiple Access - OFDM-based Modulation IEEE a - Multi-band OFDM - Direct Sequence UWB SDR UWB Solution SDR and UWB

What is UWB?

The IEEEXplore History of UWB :

FCC Definition :

UWB Spectral mask :

FCC Definition :

UWB Signaling :

Impulse Radio : Pulse shapes : Gaussian, Hermetian families

UWB Advantages : Ability to share the frequency spectrum coexistence of UWB signals with narrowband and wideband signals in the RF spectrum Large channel capacity

UWB Advantages : Ability to work with low SNRs the shannon formula indicates that the channel capacity is only logarithmically dependent on SNR. Low probability of intercept or detection because of their low average transmission power, UWB systems have an inherent immunity to detection and interception. Resistance to jamming no jammer can jam every frequency in the UWB spectrum at once.

UWB Advantages : High performance in multipath channel

UWB Advantages : Superior penetration properties the low frequencies included in the broad range of UWB frequency spectrum have long wavelength, which allows UWB signals to penetrate a variety of materials. Simple tranceiver architecture

UWB Challenges : Pulse shape distortion Channel estimation the received signal power will decrease quadratically. High-frequency synchronization very fast ADCs required. Short range low transmission power.

UWB Challenges : Multiple access interference detecting the desired user’s information is more challenging than in narrowband communication.

UWB Applications : Wireless communication systems Home networking / PAN Roadside info-station Military communications Short range radios Wireless sensor networks High-resolution RADAR and sensing vehicle RADAR see-through-the-wall (police,fire,rescue) Medical imaging Ground penetrating RADAR Surveillance Location finding RFID Position location

Modulation Types : Time-Hopping PPM Single-carrier-Based Modulation : Amplitude Modulation Orthogonal Pulse Modulation (OPM) Pseudochaotic TH-PPM

Modulation Types : OFDM-Based Modulation : The UWB frequency band is divided into multiple smaller bands with bandwidths greater than 500 MHz.

Multiple Access : FDMA : Smaller bands must be greater than 500 MHz. TDMA : CDMA OPMA (Orthogonal Pulse Multiple Access) Synchronization becomes more difficult and complicate. - The multiple access channel will achieve full user capacity when the number of users N u < 15, and when the number of users is greater, user capacity will decrease.

Multiple Access :

IEEE :

IEEE a : March 2003: more than 30 proposals were submitted to TG3a 7 proposals was chosen initially After “down selection procedure”, 2 merged proposals left: Direct Sequence Ultra Wideband (DS – UWB) & Multi-Band OFDM (MB-OFDM)

DS-UWB :

MB-OFDM :

Overview of Proposals:

SDR and UWB : 1 ) Reduce the development cycle and time-to-market Benefits of SDR for UWB : 2 ) As UWB aims at answering many needs, it may also be implemented in many flavors. Hence it would naturally gain a great benefit in supporting SDR features. 3 ) The SDR approach may also be a catalyst for new ideas and applications around UWB, thanks to its intrinsic scalability and mutability properties. At least could it permit to provide systems with adaptability features.

4 ) DS-CDMA and OFDM are sources of strong oppositions and SDR is foreseen as a solution to accommodate the different proposals. It might not make those different systems compatible, but could at least make them co-exist on the same hardware. SDR and UWB : Benefits of SDR for UWB : 5 ) Ad-hoc networking is also considered as one of UWB's great impacts. In this context, UWB systems could be adapted to support some network responsibilities through SDR techniques. Each corresponding configuration could be directly dimensioned depending on the context of ad-hoc networking really needed. This is more flexible than preinstalled general purpose configurations that are either overdimensioned or too weak.

3 ) Cost SDR and UWB : Challenges of SDR for UWB : 2 ) Power consumption 1 ) Large bandwidths which demands very high sampling rates.

SDR and UWB : Necessity to reorient SDR for UWB : Using the SDR analog front-end to do as much of the processing a possible so a narrower bandwidth digitization becomes possible Digitalizing the bandwidths of several GHz results extra cost.

SDR and UWB : Necessity to reorient SDR for UWB : - Passive analog front-end (low cost and low power consumption). - Easy-to-integrate. - Pre-processing that only extracts the necessary metrics. - Adequate bandwidth for low-cost ADCs and realistic digital processing speed. - Relaxed synchronization means. - Multiple usage of the same RF front-end output for several applications managed by SDR. - Multiband support for high data rates (each band having convenient characteristics for SDR capabilities) in a way that allows for parallelization of the subsequent digital processing.

SDR and UWB : Non-coherent elementary receiver : thus a receiver working as an energy detector, information is preferably carried by signal amplitude rather than its phase. it leads us to consider pulse amplitude modulation (such as OOK). Relaxed channel estimation Suitable signal processing Simple hardware architecture Only approximate delay spread and energy levels are needed

SDR UWB solution: General points : To increase the system capacity while preserving these properties, we propose to duplicate this basic scheme on several separate subbands (in practice from eight to 24 bands of 250 to 500 MHz each). Each band must only keep sufficient wideband characteristics to provide the receiver with enough multipath to benefit from the diversity offered by the channel. only a coarse synchronization is needed (an error of 2 ns << Ti = 40 ns is acceptable), which makes the system robust against the clock jitter and every triggering inaccuracy. Because the processing is based on energy, the transceiver performances are nearly insensitive to distortion and phase non-linearities of device. low-power consumption is achieved, thanks to the use of mainly analog and passive devices.

SDR UWB solution: Transmitter : Bank of filter Bank of local oscillator (coherence is not required) An interesting feature to notice here is that the architecture permits a simple power control in each sub-band. This kind of flexibility can be useful to fulfill a regional power spectral density mask.

SDR UWB solution: Transmitter : All the components requires are available on the shelves. We have two problems : 1- Wideband antenna 2- Insertion loss of switches

SDR UWB solution: Receiver : The integrators have to be able to integrate these signals over a time period of 10 to 50 ns. With advances in process technology, it is possible to integrate both these functions on a single chip.

SDR UWB solution: Results : As a conclusion, the proposed architecture for high data rates only requires a simultaneous digitization on each sub-band (24 as an example) at a rate of a several tens of megahertz with a resolution of one to a few bits. Indeed, comparison with coherent systems show that, to compete with our on-off keying scheme, a classical rake receiver for a coherent BPSK should collect up to 40% of the whole available energy. This is challenging due to severe multipath characteristics for typical UWB impulse radio signals and should hardly be achievable at the same cost of the solution proposed in this article.

3 - Ultra wideband wireless communications and networks X. shen, M. Guizani, R.C. Qiu, T. Le-Ngoc References : 4 - Several slides from : Ultra wideband communications past,present,future by : chris snow Ultra wideband applications and technologies by : nathania august Ultra wideband radio design by : lawrenc williams 1 - “ RF Front-End Considerations For SDR Ultra-wideband Communications systems” By Stéphane Paquelet, Christophe Moy and Louis-Marie Aubert 2 - “ A SDR Ultra-Wideband Impulse Communication System For Low And High Data Rates “ Christophe Moy - Ph.D, Stéphane Paquelet,Alexis Bisiaux - Ph.D., Apostolos Kountouris - Ph.D

Thank you for your attention! Questions?