| 摘要 |
<p>A message signal which is to be securely communicated is encoded in a wireless communications system, using a preselected code, to generate an encoded signal. A radio frequency signal (RF) representative of the encoded signal is transmitted, wherein the radio frequency signal (RF) may propagate beyond the predetermined boundary (62). A code signal (CODE) representative of the preselected code is also transmitted, wherein the propagation of the code signal (CODE) is confined within the predetermined boundary (62). At a corresponding receiver (70 and 72) within the predetermined boundary (62), the code signal (CODE) and radio frequency signal (RF) are received. The encoded signal represented by the radio frequency signal (RF) is decoded based upon the preselected code in order to recover the message signal.</p> |
