Cdma standard network architecture

CDMA - Multiple Access Methods

Frequency division duplexA duplex technique whereby uplink and downlink transmissions use two separate frequency bandsЮ

• Uplink - 1920 MHz to 1980 MHz
• Downlink - 2110 to 2170 MHz
• Bandwidth - each carrier is located in the center of a wide 5 MHz
• bandwidthUplink - 1920 MHz to 1980 MHz
• Downlink - 2110 to 2170 MHz
• Bandwidth - each carrier is located in the center of a wide 5 MHz bandwidth

Multiple Access Methods

• A radio bearer is a communication medium shared by multiple users in a geographic area. Mobile stations compete with each other for the frequency resource to transmit their traffic. Without other measures to control the simultaneous access of multiple users, collisions can occur. Since collisions are undesirable for connection oriented communications such as mobile phones, personal / mobile subscriber stations must be allocated to dedicated channels on demand.

picture 6
BS and Mobile station

Time Division Duplex

• Time division duplexing is a technique by which uplink and downlink transmissions are transmitted on the same frequency using synchronized time slots. The carrier uses a 5 MHz bandwidth, although 3GPP is investigating a low chip rate solution (1.28 Mbps). The available frequency bands for TDD will be 1900-1920 MHz and in 2010 2025 MHz.

Picture 7
duplex mode

CDMA - Channels

• Direct channelThe forward link is the communication direction or downlink path between cells. Includes the following channels
• Pilot channel. The pilot channel is the reference channel. It uses the mobile station to acquire time and as a phase reference for coherent demodulation. It is transmitted continuously by every base station on every active CDMA frequency. And each mobile station constantly monitors this signal.
• Synchronization Channel - The synchronization channel transmits one repetitive message that provides information about the time and system configuration of the mobile station. Likewise, a mobile station can have accurate system time through short code synchronization.
• Paging channel. The main purpose of a paging channel is to send pages, that is, notifications of incoming calls, to mobile stations. The base station uses these pages to transmit system overhead and messages specific to the mobile station.
• Forward Traffic Channel - Forward Traffic Channels are code channels. It is used to assign calls, usually voice and signaling traffic, to individual users.

Conclusion

The advantage of communication systems built on the principles of CDMA is the lack of frequency planning, which is necessary for efficient operation when using other methods. The capacity of this technology-based network is on average 5 times higher than in TDMA and 10 times higher than in FDMA.

References

• Collection of lectures.
• mobile-dom.ru internet site.
• ru.wikipedia.org internet site.
• Introduction to CDMA 2012 Lawrence Harte, Mike Davis