Is GSM uplink frequency greater than downlink?

[Sachin21]

HI all
In GSM, is uplink frequency is greater than downlink? if so why?

Regards
Sachin [/b]

 

[RFCMOS]

uplink and downlink frequency in gsm

Hello,

In GSM, the DL frequencies (GSM850,EGSM900....PCS) are greater than the UL frequencies. Please refer to ETSI requirements for more details or to the following link: https://en.wikipedia.org/wiki/GSM_frequency_bands

Hope this helps.

 

[ayemen]

gsm uplink frequency

also to make duplix call

 

[elbasha]

gsm uplink downlink

hi all ....
Really i need some infromation about channel coding in GSM .....

 

[Aya2002]

gsm frequency

may be the below information will help u
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The BSC–BTS interconnection is provided by 64kbit/s timeslots on 2 Mbit/s links. These 2 Mbit/s links are interfaced at the BSC by using the Terrestrial Interface Boards (MSI). Terrestrial Interface Board can interface two independent 2 Mbit/s links with each 2 Mbit/s link, providing 31 usable 64 Kbit/s timeslots, the first timeslot being used by the interfaces to synchronize the link as well as provide basic error detection.

To calculate the required number of 64 Kbit/s timeslots required between a BSC and BTS site, the site must be viewed as consisting of its own equipment and also the equipment at any sites that are connected to it. However, the amount of 64 Kbit/s timeslots to a BTS site must always be calculated so the interconnection feature can be planned.

In the GSM transmission system, the speech data between the BSC and BTS is encoded into 16 Kbit/s channels using the GSM defined format. As the E1 link utilizes 64 Kbit/s timeslots, using Sub-rate multiplexing we can allocate up to 4 X 16 Kbit/s channels per time slot. Each active Radio will have, at a BTS site, an associated Receive / Transmit Function (RTF) to send the speech data back to the BSC and the rest of the network.

Each RTF has data from 8 timeslots on the air interface therefore; it requires 2 x 64 Kbit/s timeslots on the E1 link to support its traffic data. To Support the call processing software at the BTS, the BSC must be able to send and receive control information to it.

Also this link will have to support all other controlling aspects of the BSS including statistic collection and fault reporting. This Link is the Radio Signaling Link (RSL). Each RSL uses the LAPD formatted signaling to a site and requires 1 x 64 Kbit/s timeslot or 1 X 16kbit/s Channel. Each BTS site will require a minimum of 1 LAPD signaling channel.

4.2 GSM Control Channels:-

These are:
1. Broadcast Control Channel (BCCH).
2. Common Control Channel (CCCH).
3. Dedicated Control Channel (DCCH).

4.2.1 BCCH Group:-

The Broadcast Control Channels (BCCH) is downlink only (BSS to MS) and comprises the following:
1. BCCH system information broadcasts allow the MS to correctly camp onto a cell’s transmission. These messages also contain information concerning idle neighbors.
2. The Synchronization Channel (SCH) carries information for frame synchronization and includes the BSIC.
3. The Frequency Control Channel (FCCH) provides information for carrier synchronization.

4.2.2 CCCH Group:-

The Common Control Channel Group is bi-directional i.e., it works in both uplink and downlink directions.
1. Random Access Channel (RACH) is the “uplink” used by MSs to gain access to the system.
2. Paging Channel (PCH) and Access Granted Channel (AGCH) operate in the “downlink” direction. The AGCH is used to assign resources to the MS, usually a Standalone Dedicated Control Channel (SDCCH), although a TCH can be assigned in this way. The PCH is used by the system to page a MS. The PCH and AGCH are never used at the same time.

4.2.3 DCCH Group:-

Dedicated Control Channels (DCCH) is assigned to a single MS to allow point to point signaling transactions.

1. Standalone Dedicated Control Channel (SDCCH) which supports the transfer of Data to and from the MS during call setup, location updating and Short Message Service (SMS).
2. Associated Control Channel (ACCH). This consists of slow ACCH which is used for system information, radio link measurements and power control messages. Fast ACCH is used to pass “event” type messages e.g. handover and disconnect commands. Both FACCH and SACCH operate in uplink and downlink directions.