The CDMA near far problem arises because handsets may be anywhere within the particular cell boundaries. Some handsets will be close to the base station, whereas others will be much further away. In a free space scenario signals decay according a an inverse square law...signals within a cell will have a huge variation in signal strengths. For the receiver to be able to decode all the signals in the channel, they should ideally all be at the same signal strength
I got the above information on a website while trying to understand the near-far problem. I understood the basic concept that the mobile devices near the base station will have a higher amplitude when the signal reaches the base station as compared to the ones far away. But, can't the orthogonal PN sequences used in CDMA be able to handle this. As I recall, the sequences when ex-ored with each other will produce a string of all zeros. Note that this question has already been answered here. There It has been mentioned that, the mobile phones dont have orthogonal codes. What if they did ? would that solve the near-far problem ? If not, can I know why ? Basically, In short, If 2 mobile phone signals reach the base station at different levels of power but have Orthogonal codes, wouldnt that solve the near-far problem ?