An approach to the problem of optimizing channel parameters March 2001 Vlad Oleynik, Umbrella Technology Slide 1 doc.: IEEE /152 Submission

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Parameters determining potential Throughput Rate for a given medium state Transmitter Power Level increase Signal-to-Interference Ratio (SIR) Modulation/Coding (BPSK, QPSK, MBOK, CCK, QAM...) in extreme conditions, an modulation/coding scheme with bigger redundancy (lower bit rate) may have better throughput rate Packet Length when interference is present, smaller packet length will decreased PER value Continuous medium monitoring provides the right selection and adjustment of the channel characteristics in real time mode. Slide 2

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Major determination factors Load level of the communication channel(s) STA density and topology Activity Level of WLAN distortion from other WLAN Noise Interference properties Noise bandwidth Long term / Short term Statistical analyses for medium state To estimate medium conditions, it is possible to use available measurement parameters which depend on both the mediums state and the communication channel mode. Slide 3

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Medium Changes Adaptation To perform medium monitoring it is necessary to have P sum, summary power level PhN, phase noise value PER, time frame statistics To perform medium monitoring it is necessary to have P sum, summary power level PhN, phase noise value PER, time frame statistics Packets Noise/Interference Phase Noise Threshold Psum D AB A BA F G BA D A B E A Normal receiving begins. Psum is increased. Phase Noise (PhN) is less then the threshold level B Packet has been transmitted. Psum is decreasing. Phase Noise exceeds the threshold level C Interference. Psum is increased. Phase Noise exceeds the threshold level D Power level of the packet to be transmitted is decreased due to low phase noise level of the previous packet E Power level of the packet to be transmitted is increased due to high phase noise level of the previous packet F Packet was lost because of increasing interference level during packet transmission G Packet was normally received due to high transmission power level Slide 4

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Techniques of medium adaptation Measured parameters (Psum, PhN, PER) are used to determine the set (S) of the communication channel characteristics (P, PL, Mod) which are optimal for the given regulation strategy. Demodulator IF DSSS Processor MAC PER Statistics TPC processor Received Signal Power Level P sum Modulator Phase Fluctuation Chips CLK PhN Modulation Selector Packet Length Selector S S S S Slide 5

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Techniques of medium adaptation TransmitterMedium Monitoring: PhN, PER,Psum (P, PL, Mod) Is Medium Changed? No Yes Calculation: New P, PL, Mod PhN Psum PER P Mod P, PL, Mod Updated P, PL, Mod PL Receiver Variations in medium state are represented by parameters (Psum, PhN, PER). They are the basis by which to determine the new parameter set S new = (updated Pmin/P, PL, Mod) optimized to the variable medium. Slide 6

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Techniques of medium adaptation AP STA AP's S(AP) = (P, PL, Mod) AP adaptation process - Measures PhN, Psum, PER - Determines new AP Set(P, PL, Mod) Normal frame transmission + next AP S(STA) = (P, PL, Mod) STA - Measures PhN, Psum, PER - Determines new STA Set(P, PL, Mod) AP's transmission + next STA S(AP) = (P, PL, Mod) AP Slide 7

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Transmitter Power Control Initial points for min necessary power level calculation Slide 8

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Transmitter power level adaptation Transmitter power level adaptation is based on the forecast, which is formed by real time measurement of the propagating condition change Signal/Interference Ratio (SIR) - interference level changes involve adequate transmitter power level changes Generating a forecast of the minimum necessary power level is based on RSSI and measurement of phase noise fluctuations, taking into account PER statistics optimum transmission power level is achieved and maintained adaptation of the transmitter mode to the typical changes of the medium when affected by changing interferences Slide 9

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Packet Length Adaptation Packets Noise/Interference Phase Noise Packets Threshold Phase Noise When interference is present, smaller packet length corresponds with decreased PER value Slide 10

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Packet Length Adaptation Adaptation of the packet length is based on analysis of the recent propagating conditions as well as on the cumulative statistics-based forecast for the given modulation/coding and power level Packet length adaptation to achieve maximum throughput rate is suitable for extreme conditions. For any extreme condition it is possible to determine the right packet length to provide an advantage in throughput rate Slide 11

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Packet Length Adaptation At a sufficiently high BER value the best average throughput will be achieved by selecting optimal packet length and proper modulation/coding method (not necessarily with max bit rate). Slide 12

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Packet Length and Modulation/Coding Adaptation Light magenta zone - is throughput advantage of 1 Mbps (BER 1e-5) vs 11 Mbps (BER 1e-3) Zone between - is throughput advantage of 2 Mbps (BER 1e-4) vs 11 Mbps (BER 1e-3) Zone between - is throughput advantage of 5.5 Mbps (BER 1e-4) vs 11 Mbps (BER 1e-3) At a sufficiently high BER value and for each modulation method there is a packet length which provides the maximum Throughput Rate For the same medium the BER is different for different modulation methods, and modulations with smaller bit rates may have smaller BER values Slide 13

doc.: IEEE /152 Submission March 2001 Vlad Oleynik, Umbrella Technology Adaptation of modulation methods Adaptation of modulation methods Adaptation of modulation/coding methods is based on analysis of the current state of the medium and propagation condition forecast including multi-path channels for a given power level and packet length Switching modulation method to achieve maximum throughput rate is suitable for extreme conditions. For extreme conditions a modulation/coding scheme with bigger redundancy (less bit rate) may have the advantage in throughput rate Slide 14