UMTS Wireless Communication System (3)

Wireless Communications

Problems of UMTS:

Some countries have allocated spectrum differently from the ITU recommendations, so that the standard bands most commonly used for UMTS (UMTS-2100) have not been available. In those countries, alternative bands are used, preventing the interoperability of existing UMTS-2100 equipment, and requiring the design and manufacture of different equipment for the use in these markets. As is the case with GSM900 today, standard UMTS 2100 MHz equipment will not work in those markets. However, it appears as though UMTS is not suffering as much from handset band compatibility issues as GSM did, as many UMTS handsets are multi-band in both UMTS and GSM modes. Penta-band (850, 900, 1700 / 2100, and 1900 MHz bands), quad-band GSM (850, 900, 1800, and 1900 MHz bands) and tri-band UMTS (850, 1900, and 2100 MHz bands) handsets are becoming more commonplace.

The early days of UMTS saw problems in many countries. Overweight handsets with poor battery life were first to arrive on a market highly sensitive to weight and form factor. The Motorola A830, a debut handset on Hutchison's 3 networks, weighed more than 200 grams and even featured a detachable camera to reduce handset weight. Another significant issue involved call reliability, related to problems with handover from UMTS to GSM. Customers found their connections being dropped as handovers were possible only in one direction (UMTS → GSM), with the handset only changing back to UMTS after hanging up. In most networks around the world this is no longer an issue.

UMTS Releases:

The evolution of UMTS progresses according to planned releases. Each release is designed to introduce new features and improve upon existing ones.

§  Release 99

ü  Bearer services

ü  64 kbit/s circuit switch

ü  384 kbit/s packet switched

ü  Location services

ü  Call service: compatible with Global System for Mobile            

        Communications (GSM), based on Universal Subscriber   

        Identity Module (USIM)

ü  Voice quality features – Tandem Free Operation

§  Release 4

ü  Edge radio

ü  Multimedia messaging

ü  MExE (Mobile Execution Environment)

ü  Improved location services

ü  IP Multimedia Services (IMS)

ü  TD-SCDMA (UTRA-TDD 1.28 Mcps low chip rate)

§  Release 5

ü  IP Multimedia Subsystem (IMS)

ü  IPv6, IP transport in UTRAN

ü  Improvements in GERAN, MExE, etc.

ü  HSDPA

§  Release 6

ü  WLAN integration

ü  Multimedia broadcast and multicast

ü  Improvements in IMS

ü  HSUPA

ü  Fractional DPCH

§  Release 7

ü  Enhanced L2

ü  64 QAM, MIMO

ü  Voice over HSPA

ü  CPC – continuous packet connectivity

ü  FRLC – Flexible RL

§  Release 8

ü  Dual-Cell HSDPA

ü  Dual-Cell HSUPA

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UMTS Wireless Communication System (2)

Wireless Communications

UMTS network architecture:

(RNC)  Radio Network Controller

(MSC)  Mobile Switching Center
(UE)     User Equipment
(SGSN) Serving Gprs Support Node
(PDN)   Packet Data Network
(PSTN) Public Switched Telephony Network

Spectrum allocation:

The 2100 MHz band (downlink around 2100 MHz and uplink around 1900 MHz) allocated for UMTS in Europe and most of Asia is already used in North America. The 1900 MHz range is used for 2G (PCS) services, and 2100 MHz range is used for satellite communications. Regulators have, however, freed up some of the 2100 MHz range for 3G services, together with a different range around 1700 MHz for the uplink.

Interoperability and global roaming:

UMTS phones (and data cards) are highly portable—they have been designed to roam easily onto other UMTS networks (if the providers have roaming agreements in place).

In addition, almost all UMTS phones are UMTS/GSM dual-mode devices, so if a UMTS phone travels outside of UMTS coverage during a call the call may be transparently handed off to available GSM coverage. Roaming charges are usually significantly higher than regular usage charges. Most UMTS licensees consider ubiquitous, transparent global roaming an important issue. To enable a high degree of interoperability, UMTS phones usually support several different frequencies in addition to their GSM fallback. Different countries support different UMTS frequency bands – Europe initially used 2100 MHz while the most carriers in the USA use 850 MHz and 1900 MHz

 T-Mobile has launched a network in the US operating at 1700 MHz (uplink) /2100 MHz (downlink), and these bands are also being adopted elsewhere in the Americas.

 A UMTS phone and network must support a common frequency to work together. Because of the frequencies used, early models of UMTS phones designated for the United States will likely not be operable elsewhere and vice versa. There are now 11 different frequency combinations used around the world—including frequencies formerly used solely for 2G services.

UMTS phones can use a Universal Subscriber Identity Module, USIM (based on GSM's SIM) and also work (including UMTS services) with GSM SIM cards. This is a global standard of identification, and enables a network to identify and authenticate the (U) SIM in the phone. Roaming agreements between networks allow for calls to a customer to be redirected to them while roaming and determine the services (and prices) available to the user.

Converting from GSM/GPRS to UMTS:

From a GSM/GPRS network, the following network elements can be reused:

ü Home Location Register (HLR)

ü Visitor Location Register (VLR)

ü Equipment Identity Register (EIR)

ü Mobile Switching Center (MSC) (vendor dependent)

ü Authentication Center (AUC)

ü Serving GPRS Support Node (SGSN) (vendor dependent)

ü Gateway GPRS Support Node (GGSN)

From a GSM/GPRS communication radio network, the following elements cannot be reused:

ü Base station controller (BSC)

ü Base transceiver station (BTS)

They can remain in the network and be used in dual network operation where 2G and 3G networks co-exist while network migration and new 3G terminals become available for use in the network.

The UMTS network introduces new network elements that function as specified by 3GPP:

ü Node B (base transceiver station)

ü Radio Network Controller (RNC)

ü Media Gateway (MGW)

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UMTS Single Cell Systems  intro to UMTS Cellular Systems 1st & 2nd Generations  2nd Generation Standards UMTS Phases
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UMTS Wireless Communication System 

Wireless Communications

Definition:

The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project).

UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdma one technology.

 UMTS uses wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.

UMTS specifies a complete network system which uses, covering the radio access network (UMTS Terrestrial Radio Access Network, or UTRAN), the core network (Mobile Application Part, or MAP) and the authentication of users via SIM (subscriber identity module cards).

Interfaces:

UMTS combines three different air interfaces, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codec's.

UMTS provides several different terrestrial air interfaces, called UMTS Terrestrial Radio Access (UTRA). All air interface options are part of ITU's IMT-2000.

 In the currently most popular variant for cellular mobile telephones,

 W-CDMA (IMT Direct Spread) is used.

UMTS Radio Network Subsystem:

This is the section of the UMTS / WCDMA network that interfaces to both the UE and the core network. The overall radio access network, i.e. collectively all the Radio Network Subsystem is known as the UTRAN UMTS Radio Access Network.

The Radio Network Subsystem comprises two main components:

·        Radio Network Controller, RNC:  

     This element of the radio network subsystem controls the Node Bs that  are connected to it.

The RNC undertakes the radio resource management and some of the

mobility management functions, although not all. It is also the point at which the data encryption / decryption is performed to protect the user data from eavesdropping.

·  Node B:  

     Node B is the term used within UMTS to denote the base station transceiver. It contains the transmitter and receiver to communicate with the UEs within the cell.

In order to facilitate effective handover between Node Bs under the control of different RNCs, the RNC not only communicates with the Core Network, but also with neighboring RNCs.

UMTS Core Network:

 The UMTS core network architecture is a migration of that used for GSM with further elements overlaid to enable the additional functionality demanded by UMTS.

  

In view of the different ways in which data may be carried, the UMTS core network may be split into two different areas:

· Circuit switched elements:  

These elements are primarily based on the GSM network entities and carry data in a circuit switched manner, i.e. a permanent channel for the duration of the call.

The circuit switched elements of the UMTS core network architecture

 include the following network entities:

ü Mobile switching centre (MSC)

ü Gateway MSC (GMSC)

 · Packet switched elements:   

     These network entities are designed to carry packet data. This enables much higher network usage as the capacity can be shared and data is carried as packets which are routed according to their destination.

The packet switched elements of the UMTS core network architecture include the following network entities:

ü Serving GPRS Support Node (SGSN)

ü Gateway GPRS Support Node (GGSN)

ü Home location register (HLR)

ü Equipment identity register (EIR)

ü Authentication centre (AuC)

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UMTS Single Cell Systems  intro to UMTS Cellular Systems 1st & 2nd Generations  2nd Generation Standards UMTS Phases
Communication System Systems Communications Wireless 4G 

Continue Reading →