Traffic channels provide two-way connections between space vehicles and subscriber equipment
that support Iridium services. These channels transport the system voice and data services along
with the signaling data necessary to maintain the connection and control the services.
The uplink and downlink Traffic Channels use identical burst structures. Each burst is 8.28 ms
long and contains 414 channel bits. The bursts are divided into four major data fields: Preamble,
Unique Word, Link Control Word and Payload Field. The preamble and unique word are used in
the receiving demodulator for burst acquisition. The preamble and unique word patterns are
different for the uplink and downlink. The Link Control Word provides a very low data rate
signaling channel that is used to support link maintenance, the associated control channel and
Page 19
handoff. The payload field furnishes the primary Traffic Channel that carries the mission data
and signaling messages.
The Link Control Word field provides a low rate signaling channel used for control of the
subscriber link. The uplink and downlink Traffic Channels use the same Link Control Word
format. The Link Control Word is used to support link maintenance, handoff and the ACK/NAK
of the associated control channel transmission protocol. The Link Control Word field is
protected by forward error control (FEC) code.
The Traffic Channel payload field provides the primary Traffic Channel. This field carries the
mission data and mission control data. This field supports a channel bit rate of 3466.67 bps.
Typically error correction coding and other overhead functions provide a nominal information
throughput on this channel of 2400 bps.
Mission data may be either vocoded voice data or data services. For voice service, the
proprietary Iridium vocoder uses FEC to ensure good (based on mean opinion score for a basic
telephony voice call, where 1 is bad and 5 is excellent, good is roughly a 4), or adequate, quality
vocoded voice performance tailored for the Iridium communication channels. For data service,
the L-band transport employs a frame check sequence to provide essentially error free data
transport service.
The basic interface to the SDU and the circuit switched channel setup/teardown are provided at a
modem application level using the Iridium AT command set2. Some Iridium data services also
provide additional service specific interfaces to facilitate user access. In summary, the Iridium
communication channel appears to the end users as an efficient and reliable data transport.
ممنون میشم برام تا دوشنبه ترجمش کنید...
that support Iridium services. These channels transport the system voice and data services along
with the signaling data necessary to maintain the connection and control the services.
The uplink and downlink Traffic Channels use identical burst structures. Each burst is 8.28 ms
long and contains 414 channel bits. The bursts are divided into four major data fields: Preamble,
Unique Word, Link Control Word and Payload Field. The preamble and unique word are used in
the receiving demodulator for burst acquisition. The preamble and unique word patterns are
different for the uplink and downlink. The Link Control Word provides a very low data rate
signaling channel that is used to support link maintenance, the associated control channel and
Page 19
handoff. The payload field furnishes the primary Traffic Channel that carries the mission data
and signaling messages.
The Link Control Word field provides a low rate signaling channel used for control of the
subscriber link. The uplink and downlink Traffic Channels use the same Link Control Word
format. The Link Control Word is used to support link maintenance, handoff and the ACK/NAK
of the associated control channel transmission protocol. The Link Control Word field is
protected by forward error control (FEC) code.
The Traffic Channel payload field provides the primary Traffic Channel. This field carries the
mission data and mission control data. This field supports a channel bit rate of 3466.67 bps.
Typically error correction coding and other overhead functions provide a nominal information
throughput on this channel of 2400 bps.
Mission data may be either vocoded voice data or data services. For voice service, the
proprietary Iridium vocoder uses FEC to ensure good (based on mean opinion score for a basic
telephony voice call, where 1 is bad and 5 is excellent, good is roughly a 4), or adequate, quality
vocoded voice performance tailored for the Iridium communication channels. For data service,
the L-band transport employs a frame check sequence to provide essentially error free data
transport service.
The basic interface to the SDU and the circuit switched channel setup/teardown are provided at a
modem application level using the Iridium AT command set2. Some Iridium data services also
provide additional service specific interfaces to facilitate user access. In summary, the Iridium
communication channel appears to the end users as an efficient and reliable data transport.
ممنون میشم برام تا دوشنبه ترجمش کنید...