Project: IEEE P Working Group for Wireless Personal Area Networks (WPANS) Submission Title: [Power Control and Automatic Frequency Offset Control for UWB communications] Date Submitted: [July 2003] Revised: [] Source: [Sang-sung Choi, Cheol-Ho Shin, Il-Kyoo Lee, Hyung-Soo Lee, Chang-Joo Kim] Company [Electronics and Telecommunications Research Institute] Address [161 Gajeong-dong, Yuseong-gu, Daejeon, Korea] Voice : [ ], FAX : [ ], Re: [Technical contribution] Abstract: [This presentation presents power control algorithm based on PER and the frequency offset control scheme for UWB communications] Purpose: [Technical contribution to propose power control algorithm and automatic frequency offset control method] Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual or organization. The material in this document is subject to change in form and content after further study. The contributor reserves the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P July 2003 doc.: IEEE /275r0

Submission doc.: IEEE /275r0 July 2003 ETRISlide 2 Power Control and Automatic Frequency Offset Control for UWB communications Sang-Sung Choi Cheol-Ho Shin Il-Kyoo Lee Hyung-Soo Lee Chang-Joo Kim

Submission doc.: IEEE /275r0 July 2003 ETRISlide 3 Objectives For reducing interference to other piconets and power consumption in UWB communications, a power control is required -In this presentation, we propose the power control algorithm based on Packet Error Rate (PER) to determine the optimum SIR in various interference environments To perform the coherent communication and guarantee QoS in UWB communications, we discuss an automatic frequency control scheme - Frequency offset between transmitter and receiver is one of main factors causing performance degradation in packet communications because it is accumulated within the payload duration of packet. In this study, we have analyzed the energy loss caused by the frequency offset and are now investigating some AFC algorithms

Submission doc.: IEEE /275r0 July 2003 ETRISlide 4 Power Control based on PER

Submission doc.: IEEE /275r0 July 2003 ETRISlide 5 Power Control of IEEE MAC Maximum transmitter power control - The piconet coordinator (PNC) may choose a maximum transmit power level by considering the size of piconet - The PNC shall convey this information to the DEVs via the beacon frames using the Max TX Power Level field in the beacon Octets: PNC address PNC response Piconet mode Max TX power Level CAP end time Super frame duration Time token

Submission doc.: IEEE /275r0 July 2003 ETRISlide 6 Power Control of IEEE MAC Adjustable transmitter power control -Each DEV participating in a Channel Time Allocation (CTA) may request that the other DEV with which it is communicating in the CTA either increase or decrease its transmitting power level

Submission doc.: IEEE /275r0 July 2003 ETRISlide 7 Motivations UWB Channel Characteristics - Assume fixed communications MAC Protocol - Comply to IEEE MAC -> Power Control algorithm based on PER is recommended in order to reduce interference and power consumption in UWB communications

Submission doc.: IEEE /275r0 July 2003 ETRISlide 8 Power Control Algorithm based on PER

Submission doc.: IEEE /275r0 July 2003 ETRISlide 9 Power Control Algorithm based on PER (cont.) 1. Initial SIR : The PNC may choose a maximum transmit power level using the Max TX Power Level field in the beacon 2. Check the PER within DP(Check duration of PER). (Desirable packet error rate for UWB communications is 8%) If PER is not satisfied, while(B -> G) Increase Target SIR as one-step size Target SIR = Target SIR + Send MLME-TX-POWER-CHANGE.req else while(G -> B) : Promised process Target SIR = Target SIR – TX-Power = TX-Power – Choose New Target SIR Target SIR = Target SIR + Send MLME-TX-POWER-CHANGE.req

Submission doc.: IEEE /275r0 July 2003 ETRISlide 10 Power Control Algorithm based on PER (cont.) 3. Check the PER within DP(Check duration of PER) and count the Number of Successive G(L) If L<M, Increase Target SIR as one-step size Target SIR = Target SIR + Send MLME-TX-POWER-CHANGE.req else Decrease Target SIR as one-step size Target SIR = Target SIR - Send MLME-TX-POWER-CHANGE.req where, M is the preset number of successive G 4. Repeat Process 3

Submission doc.: IEEE /275r0 July 2003 ETRISlide 11 Automatic Frequency Offset Control

Submission doc.: IEEE /275r0 July 2003 ETRISlide 12 Frequency stability in packet communications The number of symbol (1024 Octet data bits) Energy loss 0.1 LO frequency 1 LO frequency The cumulative energy loss within the payload duration is more important than the one symbol energy loss in packet communications The local oscillator with a few ppm of frequency stability for UWB communications may be used to achieve low cost device. The cumulative energy loss within the payload duration may be serious as shown in the figure.

Submission doc.: IEEE /275r0 July 2003 ETRISlide 13 Simulation for the frequency stability of UWB communications Consider the parameters of UWB communications to analyze the frequency stability in packet communications parametersvalue Symbol duration  ns ModulationBPSK/QPSK Payload length1024 Octet Payload duration   s

Submission doc.: IEEE /275r0 July 2003 ETRISlide 14 Cumulative Energy Loss in 1024 Octet data bits : 0.1 : 0.4 : 0.5

Submission doc.: IEEE /275r0 July 2003 ETRISlide 15 Average Energy Loss within the Payload Duration Frequency offset Average Energy Loss(dB) The frequency offset between TX and RX results in energy loss - The tolerance of frequency offset is related to the payload duration of packet

Submission doc.: IEEE /275r0 July 2003 ETRISlide 16 Frequency Offset Control Scheme Architecture of digital feedback frequency offset control - Frequency offset acquisition The phase difference between 2 successive samples gives an indication of the frequency offset Refered to IEEE802.11b Receiver Design Nov.30,2001 by cadence

Submission doc.: IEEE /275r0 July 2003 ETRISlide 17 Frequency Offset Control Scheme (cont.) Architecture of digital feedback frequency offset control - Frequency offset tracking A data-directed digital PLL may be used to track the residual frequency offset Refered to IEEE802.11b Receiver Design Nov.30,2001 by cadence

Submission doc.: IEEE /275r0 July 2003 ETRISlide 18 Summary For reducing interference to other piconets and power consumption, a power control is required - Power control based on PER is appropriate because the Target SIR is determined by the actual received SIR In the packet communications, the frequency offset would cause serious energy loss if it is not corrected properly - The stability of frequency offset has been analyzed -The frequency offset control scheme is under study