Method for optimizing the random access procedures in the cdma cellular networks
First Claim
1. A random access procedure in a cellular telephony system based on the so-called CDMA technique by which individual coding sequences each other orthogonal are respectively assigned to both a base station (BTSC) and the served mobile stations (MS, UE) for spread-spectrum modulating an uplink carrier and de-spreading demodulating a downlink carrier, in order to support a variety of service physical control channels for providing synchronisation, signalling and services and conseguently enabling a reliable two-way communication, said physical control channels including:
- synchronisation channels constituted by signature bursts (SYNC1) valid into the serving cell, randomly selected by the mobile stations and transmitted for gain uplink synchronisation and power adjustment;
forward access channels (P-FACH, FACH) carrying towards the mobile stations the so-called physical information suitable to adjust timing and power level of the transmitters;
random access common channels (P-RACH, RACH) acceded by the mobile stations intending to send their channel requests to the network;
access grant channels (P/S-CCPCH, AGCH) containing the configuration parameters of dedicated service channels (DPCH) together with the network answers to any correctly detected and accepted channel request message;
broadcast channels (P/S-CCPCH, BCCH) for diffusing the system information (BCCH) inside the serving cell about number and configuration parameters of the said provided physical control channels estimated according to the traffic expected to serve through them by the serving cell, characterized in that it includes;
a preliminary step adapted to establishing associations between the configuration parameters of said physical control channels, and actual steps adapted to exchange protocol messages with the network (BSSC, MSC), said associations carried out in the course of said preliminary step including;
one signature burst (SYNC1) being associated to one forward access channel (P-FACH) only, repeating the association for all the uplink synchronisation channels, in order to avoid any ambiguity in the mobile stations about where to look for the expected acknowledgement from the network;
one random access common channel (P-RACH) being associated to one forward access channel (P-FACH) only, repeating the association for all random access common channels, in order to reduce collision on the latter (P-RACH);
one access grant channel (P/S-CCPCH, AGCH) only being associated to one random access common channel (P-RACH), repeating the association for all the access grant channels (P/S-CCPCH, AGCH), in order to avoid any ambiguity in the mobile stations about where to look for the expected answer from the network with the indication of the dedicated service channels (DPCH); and
said actual steps including;
broadcasting into the serving cell to be read by the mobile stations (MS, UE) each complete associative link binding the involved physical channels;
exchanging protocol messages with the network (BSSC, MSC) through said associative links in order to signalling at once to the mobile stations the route towards the services offered by the network, simplifying the access procedure consequently.
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Abstract
The disclosed invention is referred to a method for optimising the random access procedures in third generation CDMA cellular telephony systems. The particular embodiment of the example concerns a TD-SCDMA-TDD synchronous realization. The disclosed procedure includes a preliminary part charged to the network (BSSC, MSC) only for establishing the following associations between the configuration parameters of the involved physical channels:
one signature burst (SYNC1) is associated to one forward access channel (P-FACH) only, in order to avoid any, ambiguity in the mobile stations about where to look for the expected acknowledgement from the network;
one random access common channel (P-RACH) is associated to one forward access channel (P-FACH) only, in order to reduce collision on the latter (P-RACH);
one access grant channel (P/S-CCPCH, AGCH) only is associated to one random access common channel (P-RACH), in order to avoid any ambiguity in the mobile stations about where to look for the expected answer from the network with the indication of the dedicated service channels (DPCH); and
each complete associative link binding the involved physical channels is included in the system information and broadcasted into the serving cell to be read by the mobile stations (MS, UE) when entering an actual part of the procedure charged to exchange protocol messages with the network (BSSC, MSC) through said associative links that being signalling at once to the mobile stations the route towards the services offered by the network, simplifying the access procedure consequently.
Suitable groupings among: Downlink pilot sequences, Uplink pilot sequences, scrambling codes, basic midambles, are carried out in a cell-discriminating way and broadcasted into the cell to simplify the serving cell selection procedure (FIG. 1).
345 Citations
14 Claims
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1. A random access procedure in a cellular telephony system based on the so-called CDMA technique by which individual coding sequences each other orthogonal are respectively assigned to both a base station (BTSC) and the served mobile stations (MS, UE) for spread-spectrum modulating an uplink carrier and de-spreading demodulating a downlink carrier, in order to support a variety of service physical control channels for providing synchronisation, signalling and services and conseguently enabling a reliable two-way communication,
said physical control channels including: -
synchronisation channels constituted by signature bursts (SYNC1) valid into the serving cell, randomly selected by the mobile stations and transmitted for gain uplink synchronisation and power adjustment;
forward access channels (P-FACH, FACH) carrying towards the mobile stations the so-called physical information suitable to adjust timing and power level of the transmitters;
random access common channels (P-RACH, RACH) acceded by the mobile stations intending to send their channel requests to the network;
access grant channels (P/S-CCPCH, AGCH) containing the configuration parameters of dedicated service channels (DPCH) together with the network answers to any correctly detected and accepted channel request message;
broadcast channels (P/S-CCPCH, BCCH) for diffusing the system information (BCCH) inside the serving cell about number and configuration parameters of the said provided physical control channels estimated according to the traffic expected to serve through them by the serving cell, characterized in that it includes;
a preliminary step adapted to establishing associations between the configuration parameters of said physical control channels, and actual steps adapted to exchange protocol messages with the network (BSSC, MSC), said associations carried out in the course of said preliminary step including;
one signature burst (SYNC1) being associated to one forward access channel (P-FACH) only, repeating the association for all the uplink synchronisation channels, in order to avoid any ambiguity in the mobile stations about where to look for the expected acknowledgement from the network;
one random access common channel (P-RACH) being associated to one forward access channel (P-FACH) only, repeating the association for all random access common channels, in order to reduce collision on the latter (P-RACH);
one access grant channel (P/S-CCPCH, AGCH) only being associated to one random access common channel (P-RACH), repeating the association for all the access grant channels (P/S-CCPCH, AGCH), in order to avoid any ambiguity in the mobile stations about where to look for the expected answer from the network with the indication of the dedicated service channels (DPCH); and
said actual steps including;
broadcasting into the serving cell to be read by the mobile stations (MS, UE) each complete associative link binding the involved physical channels;
exchanging protocol messages with the network (BSSC, MSC) through said associative links in order to signalling at once to the mobile stations the route towards the services offered by the network, simplifying the access procedure consequently. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification