This region contains wide and na,rrow streets with low and high buildings and is representative of the heavily built-up downtown areas of many large cities in the United St.ates.The dist.ribut,ion of d indicates that the a.vera,ge error experienced by a CW ranging system would be >600 m over 10 percent. of t,he region. As an example of communications system limitations implied by the dist.ribut.ion of s, the bit rate for digital transmission cannot exceed 3012 bits!s if the irreducible error rate is to remain below 10-3 over 90 percent of the region. ACKXOWLEDGMENTWe wish t,o thank

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