The user then decides to make a call. The number is keyed in and the send key is hit. This initiates an Access Probe. The mobile uses a special code channel called the Access Channel to make contact with the cell site. CDMA mobiles can transmit two types of channels on the single physical channel … Read more
What is inside PAGING Channel Message in CDMA The paging channel is the heart of a CDMA base station. All of the parameters and signaling necessary for the proper operation of a CDMA cell site are handled by the paging channel. The paging channel supports a number of distinct messages that provide information and send … Read more
The sync channel messages include the CDMA protocol revision supported by the cell site, the minimum protocol revision supported by a CDMA mobile in order to work with the cell site, the system and network identification numbers for the cell site, the PN offset of the cell site, the paging channel data rate, and all … Read more
System Access: When the mobile first turns on, it must find the best base station. This is similar to analog where the phone scans all the control channels and selects the best one. In CDMA, the mobile unit scans for available Pilot signals, which are all on different time offsets. This process is made easier … Read more
The original release of the EIA/TIA-95-B standard defined the protocol messages and formats to be used in the CDMA system. This release is know as Revision 0 of the IS-95 standard. Since the release of Revision 0, a newer standard has been released for cellular CDMA that is called the Revision A standard of IS-95. … Read more
A number of different service options have been defined for use on the CDMA physical channel. A description of each of the service options follows: Service Option 001 – This is the normal, duplex voice conversation mode that uses the original 8 kbps vocoder defined in the TIA IS-96-A specification. Service Option 002 – This … Read more
Forward – Reverse Link Advantages – Disadvantages CDMA The forward link advantages include high transmission power, a pilot channel to provide a timing reference as well as a coherent reference to aid in demodulation, the added time diversity of data bit repetition when transmitting at lower voice data rates, and orthogonal code channel. On the … Read more
The CDMA reverse link uses a different coding scheme to transmit data. Unlike the forward link, the reverse link cannot support a pilot channel for synchronous demodulation (since each mobile station would need its own pilot channel). The lack of a pilot channel is partially responsible for the reverse link’s lower capacity than the forward … Read more
If the modulation data changes, QPSK modulation makes one symbol change each period. If the data is the same, then QPSK and OQPSK do not change state. However, if the data changes, then OQPSK will make at least one symbol change and possibly two changes in a single period. QPSK Makes one Symbol Change Every … Read more
Reverse Channel Long Code Spreading The channelization in the reverse link must provide for unique code assignments for every operational phone. Long Code Spreading Provides Unique Mobile Channelization Mobiles are Uncorrelated but not Orthogonal with Each Other Since the long code is 42 bits in length, this allows 2^42 (4.3 billion) unique channel assignments. Thus … Read more