Definition
The channel is the channel for transmitting information. Physical channels generally refer to channels that rely on physical media to transmit information, such as telephone lines, optical fibers, coaxial, microwaves, etc. Logical channels generally refer to artificially defined information transmission channels. Roughly more, most of them are coded or divided into different time slots to transmit different information.
Classification of IS95 physical channels
Forward channel td> | Pilot channel (Pilot) |
Sync channel (Sync) | tr>|
Paging channel (Paging) | |
Traffic channel (Traffic) | |
Reverse Channel | Access Channel (Access) td> |
Traffic |
Pilot channel< /p>
The pilot channel is the basis for the mobile terminal to establish communication with the base station. It uses Walsh code 0 (Walsh #0) spread spectrum and transmits a signal of all 0s. The pilot channel adopts PN short code offset. The PN short code is used to distinguish different sectors in the forward direction. There are 512 PN short code offsets that can be used in the CDMA system, and each PN short code offset is used to identify a specific sector.
The main function of the forward pilot channel is twofold:
It is used for the initial acquisition of the terminal and helps the mobile terminal to find the base station.
When the mobile terminal is turned on, it first searches for the pilot channel, and then demodulates the synchronization channel by capturing the pilot channel.
When the mobile terminal is in the communication state, the auxiliary terminal switches.
When switching, the mobile terminal measures and compares the channel strength of each pilot channel as a basis for judging whether to switch.
Sync Channel
The bit rate of information transmitted on the sync channel is 1200 bps. The synchronization channel uses Walsh code #32 (Walsh #32) to spread each modulation symbol.
The main functions of the forward synchronization channel are:
Get system time
The base station time synchronization can ensure the subsequent correct demodulation of the transmitted signal, and the mobile terminal performs time synchronization with the base station through the synchronization channel. The mobile terminal will receive the synchronization channel information only when the mobile terminal is powered on and initialized or after each call ends.
Provide paging channel rate
Provide basic system parameters
Calculate the initial state of PN offset and PN long code
Paging channel
The base station uses the forward paging channel to send system overhead information to all mobile terminals. After selecting the serving base station, each mobile terminal also listens to the paging message sent by the base station through the paging sub-channel belonging to it.
The forward paging channel adopts Walsh code #1 (Walsh #1) spread spectrum, as the basic paging channel, supporting two transmission rates of 9600 bps or 4800 bps. A single CDMA carrier frequency can support up to 7 paging channels, and other additional paging channels are spread by Walsh #2~ Walsh #7. The unused paging channel can be used as a forward traffic channel.
The functions of the forward paging channel are:
Send paging messages
Send overhead information :
1) System message
2) Neighbor cell list
3) Frequency band list
4) Extended system message: switching message , Power control message
traffic channel
During a call, the service channel is used to send user service information and related signaling to a specific mobile terminal. The service channel is different from the Wharf code used by the pilot channel, synchronization channel, and paging channel. The pilot channel uses Walsh#1, the synchronization channel uses Walsh#32, the paging channel uses Walsh#1~7, and the traffic channel uses the remaining Walsh codes among the 64 Walsh codes. Therefore, the maximum number of traffic channels is: 64 minus one pilot channel, one synchronization channel, and one to seven paging channels. That is, each carrier frequency of CDMA can have up to 61 service channels. Usually the number of traffic channels does not exceed 40.
The functions of the forward service channel are:
Send user service packages
Send service related Signaling
Different from other physical channels, there are also traffic channels in the direction from the terminal to the base station. The role of the reverse traffic channel is similar to that of the forward traffic channel, including:
Send user service packages
Send user pairs from Base station's command and query response
Send user's request to the base station
< /p>
Access Channel
The mobile terminal uses the reverse access channel to establish initial communication with the base station and respond to messages on the paging channel. Each access channel is only related to one paging channel, and each paging channel can support up to 32 access channels. The reverse access channel rate is fixed at 4800 bps.
The role of the reverse access channel is as follows:
Send paging message
Paging response
Registration during idle handover or inter-cell
CDMA2000 1X physical channel
Physical Channel | CDMA2000 1X | IS95 | ||
Forward Channel | Pilot channel (F-Pilot) | Pilot channel (Pilot) | ||
Sync channel (Sync) | ||||
Paging channel (Paging) | Paging channel (Paging) | |||
Business channel ( Traffic) | Traffic channel (Traffic) | |||
Supplementary Channel (F-SCH)< /p> | ||||
Reverse channel | Access | Access channel (Access) | ||
Traffic channel (Traffic) | Traffic channel (Traffic) | |||
Pilot channel (R-Pilot) td> | ||||
Supplementary Channel (R-SCH) |
Physical channel | CDMA2000 1X | CDMA2000 DO | ||
Forward Channel | Pilot Channel (F-Pilot) | Pilot channel (Pilot) | It has the same function as 1X pilot channel. | |
Sync channel (Sync) | Control channel< /p> (Control) | It is used to carry system control messages, which is equivalent to the combination of synchronization channel and paging channel in 1X. | ||
Paging channel (Paging) | ||||
Traffic channel (Traffic) | has the same function as 1X traffic channel. | |||
Supplementary Channel (F-SCH) | Media Access control channel (MAC) | Reverse power control sub-channel (RPC) td> | is used to transmit reverse traffic channel power control information. | |
ARQ subchannel | Used to indicate whether the reverse traffic channel is demodulated correctly Data packet. | |||
DRCLock subchannel | Used to respond to the DRC subchannel in the reverse channel, Feed back the link quality of the current serving sector to the terminal. | |||
Reverse activation subchannel (RA) | Used to send a reverse link activation indication. Indicate the current reverse busy/idle status, which determines the reverse transmission rate of the terminal. | |||
Reverse channel | Access channel (Access ) | Access channel (Access) | Pilot channel < p>(Pilot) | Used for coherent demodulation and timing synchronization of the reverse link. |
Data channel (Data) | Used to carry Access the packet data of the channel. | |||
Traffic channel (Traffic) | Traffic channel< /p> (Traffic) | Pilot channel (Pilot) | Used for coherent demodulation and timing synchronization of the reverse link. | |
Pilot channel (R-Pilot) | Auxiliary pilot channel (Aux) | It is used to assist the base station in the channel estimation of the reverse link. Used when the transmission rate is greater than or equal to 76.8 kbps. | ||
Supplementary Channel (R-SCH) | Media Access control channel (MAC) | Reverse rate indicator sub-signal River (RRI) < /td> | is used to indicate to the base station the rate of the reverse traffic data channel currently used by the terminal. | |
Data Rate Control Subchannel (DRC) | Used after the terminal applies to the base station The rate of the forward traffic channel for sending data packets, and the sector that determines the service provided to the terminal. | |||
Data source control subchannel (DSC) | Used by the terminal to indicate to the base station that the base station service sector it has selected. | |||
ACK channel | Used to indicate whether the forward traffic channel data is demodulated correctly Package. | |||
Data channel (Data) | and 1X business The channel functions are the same. |
In the forward physical channel of CDMA2000 DO, the pilot channel, control channel, traffic channel and medium access control channel adopt a time division method . In the reverse physical channel, the access channel and the traffic channel use time division, and the pilot channel, auxiliary pilot channel, medium access control channel, ACK channel and data channel under the traffic channel use code division. .
LTE physical channel
Physical channel | LTEPhysical channel | Function | Modulation method |
| Downlink Channel | Physical Downlink Shared Channel (PDSCH, Physical Downlink Shared Channel) | Bearing downlink service data and paging messages. | QPSK, 16QAM or 64QAM |
Physical layer broadcast channel (PBCH, Physical Broadcast Channel) | It carries broadcast information and occupies 6RBs (1.08 MHz) in the middle of the carrier channel. | QPSK | |
Physical layer downlink control channel (PDCCH , Physical Downlink Control Channel) | Carries downlink scheduling information, such as channel allocation and control information. | QPSK | |
Physical layer format indicator channel (PCFICH , Physical Control Format IndicatorChannel) | It is used to indicate the number of OFDM symbols used for PDCCH transmission in a subframe. | QPSK | |
Physical layer hybrid automatic retransmission HARQ request indication channel (PHICH, Physical Hybrid Indicator Channel) | Carries HARQ information, such as ACK/NACK. | BPSK, support code division multiplexing channel | |
Physical layer multicast channel p>(PMCH, Physical Multicast Channel) | The downlink multicast channel is used to support MBMS services in a single-frequency network and bear the broadcast information of multiple cells. Multiple cells in the network send the same information at the same time and frequency band, and signals from multiple cells can be used as multipath signals for diversity reception. | QPSK, 16QAM or 64QAM | |
Upstream channel | Physical Uplink Shared Channel (PUSCH, Physical Uplink Shared Channel) | Carries uplink control information and service data. | QPSK, 16QAM or 64QAM |
Physical layer uplink control channel < p>(PUCCH, Physical Uplink Control Channel) | Carries uplink control information (UCI), such as HARQ information, ACK/NACK, CQI/PMI, RI. | BPSK or QPSK | |
Physical layer random access channel (PRACH, Physical Random Access Channel) | Used for the terminal to initiate communication with the base station. When the terminal randomly accesses, the preamble information is sent, and the base station receives it through PRACH, determines the identity of the access terminal and calculates the delay of the terminal. | QPSK |
From base station to terminal is called downlink, and from terminal to base station is called uplink . The downlink channel and the uplink channel respectively correspond to the forward channel and the reverse channel introduced earlier.
