Performance Analysis of Complementary Code Keying (CCK) Modulation in a Multi-Path ChannelPaul Yang, University of California at BerkeleySURE Program Summer 2002Advisor: Professor Daniel NoneakerMotivations/GoalsRepresentation of a Signal in the Signal SetSingle-Path AWGN ModelThe Multi-Path ChannelMulti-Path Simulation: Error Probability vs. Alpha RatioMulti-Path Simulation:Error Probability vs. Delay at High Alpha RatioMulti-Path Simulations: Error Probability vs. Delay at Low Alpha RatiosCCK is a 256-ary modulation scheme => 256 distinct signalsCoherent Correlation Detector: 256 correlators Noise: modeled by random variables (N0 ,, Nn-1)AWGN = Additive White Gaussian NoiseAnalytical Upper bound: dotted blue lineAnalytical Lower bound: dashed green lineSimulation Results: solid red lineSimulation Results for a AWGN Single-Path ChannelMulti-Path Propagation

There is a growing demand for high data access rates in wireless communications systemsSome high data rate wireless communications standards are: IEEE 802.11b, Bluetooth, etc.CCK is the modulation scheme used for IEEE 802.11bUseful property of CCK Modulation: Provides protection against phase ambiguity in receivers phase-locked loopAt high data rates, multi-path can occur, leading to performance degradationGoal: Find performance of CCK Modulation in multi-path channelTwo paths from transmitter to detectorAlpha ratio = strength of direct channel relative to indirect channel.SNR: sum of signal-to-noise ratios in both pathsFor the coherent correlation detector used in this system, the indirect path acts as a distortionFactors that decrease error probability: high alpha ratio, high SNRCCK Modulation performs well in single-path channelCCK Modulation does not achieve acceptable error probability in a multi-path channel with this detectorConclusions:Future Work:Error probability decreases with increasing alpha ratioDesired error probability = 10^(-2) => achieved at alpha ratio of 2.5 High alpha ratio = low error probability Weak Indirect Signal => Delay does not matter Same as single-path channelStart with a binary word:Use tables and formula:End up with a length 8 complex vector:Use Eulers formula to simplify:Note: Signal representation information obtained from Intersil Corp. At an alpha ratio of 1, the error probability is very high. At an alpha ratio of 3, the error probability is lower than with 1, but still high compared to the single-path channel.Low alpha ratio = high error probabilityStrong Indirect Signal => Delay matters Worst case: delay = 3Acceptable error probability: 10-2 not achieved for SNRdb = 7The coherent correlation receiver we used in this system was designed for use with high alpha ratios. Any indirect paths act as distortion. There are other types of receivers designed for use in multi-path channels, such as a rake receiver. The next logical step would be to consider CCK Modulations performance in a system with a rake receiver. Indirect path reflects off an object, and usually loses some signal energy Indirect path travels a longer distance, so its delayedAcceptable error probability: 10^(-2) achieved at 7.5 to 8 decibelsPicture obtained from International Engineering Consortium:http://www.iec.org/online/tutorialsMulti-Path Channel Model