May 2011 - Telecommunications Blog

A blog for mobile communications systems GSM , UMTS and LTE

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Saturday, May 21, 2011

WCDMA Network Planning 1

5/21/2011 12:47:00 AM 2
WCDMA Network Planning 1
Planning

     • Planning should meet current standards and demands and also comply with future requirements.
     • Uncertainty of future traffic growth and service needs.
     • High bit rate services require knowledge of coverage and capacity enhancements methods.
     • Real constraints
               – Coexistence and co-operation of 2G and 3G for old operators.
               – Environmental constraints for new operators.
     • Network planning depends not only on the coverage but also on load.

Objectives of Radio network planning

     • Capacity:
               – To support the subscriber traffic with sufficiently low blocking and delay.
     • Coverage:
               – To obtain the ability of the network ensure the availability of the service in the entire service area.
     • Quality:
               – Linking the capacity and the coverage and still provide the required QoS.
     • Costs:
               – To enable an economical network implementation when the service is established and a controlled network expansion during the life cycle of the network.

Thursday, May 5, 2011

MAC Layer in WiMAX IEEE 802.16

5/05/2011 04:11:00 PM 0
MAC Layer in WiMAX IEEE 802.16
  The MAC layer of IEEE 802.16 is designed to serve sparsely distributed stations with high data rates, where the SSs are not required to listen to the other stations like the MAC in IEEE 802.11. 

  The BS schedules the transmissions of the corresponding SSs in advance. The MAC of WiMAX is reservation-based and contention-free. The SSs need to contend only when they access the channel for the first time at the connection admission control stage. 

  The reservation-based resource allocation allows the WiMAX BS to serve a large number of SSs as well as the guarantee of QoS in the connection level for both uplink and downlink traffic. 

  Compared with 802.16, Wireless Local Area Networks (WLAN) based on IEEE 802.11 terminals usually have intermittent  traffic that contends every time before transmitting, where the efficiency is significantly impaired when more stations enter the network.


  The main purpose of the MAC protocol is the sharing of radio channel resources among
multiple accesses of different users. The MAC also contains a separate security sublayer handling authentication, secure key exchange, and encryption.

Tuesday, May 3, 2011

WiMAX IEEE 802.16 family

5/03/2011 08:08:00 PM 0
WiMAX IEEE 802.16 family
WiMAX IEEE 802.16 family :.
  •  IEEE 802.16a: The standard specifies the operation from 2GHz to 11GHz, both licensed and license exempts. Because the signals at lower frequency can penetrate barriers and thus a line-of-sight connection between the transceiver and receiver is not required, most commercial interests have focused mainly on the lower frequency ranges. Under this premise, IEEE 802.16a standard was thus completed in January 2001. It enables the WiMAX implementations with better flexibility while maintaining the data rate and transmission range. IEEE 802.16a also supports mesh deployment, which can extend the network coverage and increase the overall throughput.

  •  IEEE 802.16b:  This extension increases the spectrum to the 5 and  6 GHz frequency bands, which provides QoS guarantee to ensure priority transmission for real-time applications and to differentiate service classes for different traffic types.

  •  IEEE 802.16c: As the Work Group’s initial interest, IEEE 802.16c defines a 10 to 66 GHz system profile that standardizes more details of the technology. These high frequency bands have more available bandwidth, but the signals cannot diffract the obstacles and require line of sight deployment. 

  •  IEEE 802.16d:  Approved in June 2004, IEEE 802.16d upgrades the 802.16a
standard. This extension aims to improve performance for 802.16 especially in the
uplink traffic.

  •  IEEE 802.16e:  This technology standardizes networking between fixed base stations (BSs) and mobile base stations (MSs), rather than just between base stations and fixed recipients. IEEE 802.16e enables the high-speed signal handoffs necessary for communications with users moving in vehicles. It promises to support mobility up to speeds of 70-80mi/h. The subscriber stations (SSs) could be personal communication devices such  as mobile phones and laptops.

We will continue the family next posts .

Wireless Ad hoc Networks

5/03/2011 10:59:00 AM 1
Wireless Ad hoc Networks
  Wireless ad hoc networks have special characteristics related to node mobility, node self-configuration and the lack of centralized access points (APs). However, wireless ad hoc technologies have several disadvantages when compared to traditional wireless
networks, including their limited resources, such as:

       ** Lower processing capacity
       ** Limited memory
       ** Battery dependency

  Because operations are not centralized in a single access point, information is openly distributed among the network nodes. As a result, wireless ad hoc networks are not as secure as typical wireless networks.

  Wireless ad hoc networks are usually associated with wireless mesh networks; however, these two concepts can be dealt separately.

  The essential idea of wireless ad hoc networks is that they are mobile and dynamic. This
concept is not at all new.
Source : IEEE