Figure 3 QoS Frame of UMTS
Evolution of CN Technology
- Total IP CN
Brand UTRAN is introduced in initial phase of 3GPP R99, to reduce the influence of UTRAN on CN.
Introduction policy of CN is developed from GSM/GPRS CN.
During the evolution from R99 to R4, CN realizes the separation of CS domain control layer and transmission layer, realizes voice packet and signaling packet, transmits CS and PS domains application in CN based on one IP.
During the evolution from R4 to R5, 3GPP CN introduced IMS based on packet domain.
IMS adopts Session Initiation Protocol (SIP) that IETF defines and provides IP services that Qos is sensitive to (such as, VoIP) in packet switching domain, to intercommunicate fixed IP terminal and 3G mobile terminal.
In R6 version, functions of IMS are enhanced greatly, including the intercommunication of local IP multimedia network and other IP multimedia networks, intercommunication of IMS and CS, intercommunication of IMS based on IPV4 and IPV6, multi-party conference service, IMS group management and SIP appended to IMS.
As a result, wider and more flexible IP-based multimedia services are provided for operation.
During the evolution from R99 to R7, CN may absolutely abandon circuit switching domain in the future and develops into a total IP service mobile network.
- Network sharing
In 3GPP R99/R4, one RNC can only connect one MSC or SGSN, resulting in low utilization ratio of resources.
In R5, Iu-Flex is introduced between CN and UTRAN, realizing the UTRAN resources sharing among several nodes of one operator.
It saves the cost on UTRAN and substantially develops the network sharing technology.
In R6, network sharing function is expanded continuously, which provides the configuration mode of Multiple Operator Core Network (MOCN).
MOCN allows several operators to share one radio access network in sharing area.
As a result, operators can save investment on UTRAN.
- Amalgamation with other networks
In 3GPP R6, intercommunication and amalgamation of UMTS and WLAN are fulfilled (Phase I), which is strengthened in R7 plans (Phase II).
In addition, in R7, defines feasibility of total IP network operation.
Intercommunication and amalgamation of CN with other networks is future development trend.
Evolution of Radio Access Network Technologies
- High-speed broadband access
Compared with GSM/GPSR RAN, R99 introduced new UTRAN.
UTRAN is based on WCDMA radio interface technology.
Its signal bandwidth is 5 MHz. Its code chip rate is 3.84 Mbps.
Its cell downlink service bandwidth is about 2 M.
R4 version has no large change in radio access.
In R5 version, HSDPA is introduced. It adopts 16 QAM modulation mode, which greatly increases spectrum utilization ratio.
Cell downlink peak rate reaches 14 Mbps. In the field, the system supporting HSDPA is defaulted as 3.5 G system.
In R6 version, HSUPA is introduced, which makes cell uplink peak rate up to 5.7 Mbps.
In R7 version, Multiple Input Multiple Output (MIMO) antenna technology is introduces, which enables several transmitting and receiving antennas to send and receive signals in same band. As a result, system capacity and spectrum utilization ratio is increased in germination.
MIMO antenna technology meets the requirements for high speed services in future mobile communication system. In Long Term Evolution (LTE) items, Orthogonal Frequency Division Multiplexing ( OFDM) is introduced, which makes cell downlink peak rate up to 39 Mbps.
It may develop as the core technology base of 3G advanced system (such as, Beyond 3G, 3.9 G and E3G).
With continuous development of 3GPP standardization, OFDM will be applied to broadband mobile communication field more widely in the near future.
In the future, MIMO and OFDM technologies will combine.
System test results improve that MIMO-OFDM system which has two transmission antennas and two receiving antennas can provide the data transmission rate from score to a hundred million.
In a word, evolution process of radio access network on access bandwidth is: 2 Mbps (R99) -> HSDPA DL 14 Mbps (R5) -> HSDPA DL 14 Mbps/HSUPA UL 5.7 Mbps (R6) –> MIMO (R7) -> OFDM (LTE).
Its evolution is to introduce all kinds of technologies, increasing spectrum utilization ratio furthest and meeting the requirements for high speed data transmission.
- Mobile management
From R99 version, WCDMA has differences from GSM/GPRS in mobile management, including soft handover, Iur interface, re-positioning, handover and re selection between 2/3G.
From R4 version, Iur interface has introduced such flows as public measurement and radio link congestion, which makes radio resource management and load control of Iur interface be organic part of UTRAN.
At the same time, amalgamation criteria with GERAN are under way, including Iur-g, cell change that network aids.
- IP transmission
UTRAN in R99/R4 versions adopts TDM and ATM. CN in R4 version successfully introduces the base of IP transmission technology.
3GPP UTRAN in R5 version also introduces IP transmission technology.
IP transmission is a selective technology of UTRAN and it makes UTRAN transmit based on IP core switching network.
As a result, flexibility of transmission networking is increased and construction cost of operators is reduced.
IP transmission is also UTRAN transmission development trend.
In transmission, R4/R5 versions added transmission bearer modification and reconfiguration, to further optimize the performance of transmission bearer.
- Antenna technology
During the evolution of 3GPP standards, 3GPP also has evolution in antenna technology and antenna evolution process is:
Two projects of wave cluster figuration (R5) -> Fixed wave cluster figuration project and 3GPP electronic modulation antenna (R6) -> MIMO (R7).
The evolution is to improve link performance of the system by introducing all kinds of antenna technologies, increasing system capacity.
In R5 version, radio wave cluster figuration technology is introduced to increase system link performance and capacity.
Two projects are put forward: fixed wave cluster figuration and user special wave cluster figuration.
In R6 version, user special wave cluster figuration project is deleted and fixed wave cluster figuration project is decided.
In mobile BS network planning and optimization, common measure is to remotely modulate antennas of BS system.
Most operators purchase antennas from third party. In these years, Antenna Interface Standard Group (AISG) has put forward AISG interface standards.
However, since 3GPP does not definite antenna interfaces in R99/R4/R5 phases, it is difficulty for manufacturers to have same antenna interface, antenna type and network optimization.
Therefore, in R6 version, 3GPP uniforms interface of RET and introduces Iuant antenna interfaces.
Standardization of RET interfaces makes remote network optimization possible on condition that several manufacturers provide antennas.
In R7 version, 3GPP puts forward MIMO, which increases system capacity and spectrum utilization ratio in germinations.
Although MIMO is not mature at present, it is a great breakthrough of antenna technology in mobile communication field and also a developing direction of future intelligent antenna technology.
- Positioning technology
In R99 version, UE positioning technology based on cell ID is introduced.
It is a rough positioning technology. In R99 version, frames of OTDOA and A-GPS are introduced, too.
In R4 version, criteria of Iub/Iur interfaces are put forward, which improves OTDOA and A-GPS positioning technologies.
In R5 version, criteria of SMLC-SRNC interfaces are put forward and they are open to support A-GPS positioning technology (not supporting other positioning technologies).
In R4 and R5, lowest performance requirements for A-GPS measurement are not given.
Therefore, in R6 version, positioning precision of A-GPS is defined (positioning range of a mobile station is 30 to 100 m and response time is 2 to 20 s.
In R6 version, SMLC-SRNC interfaces are open to support three positioning technologies (Cell ID, OTDOA and A-GPS).
In R7 version, Uplink-Time Difference Of Arrival (U-TDOA) is put forward.
It is hoped to provide solutions that are more flexible and whose positioning precision is higher.
The evolution process of positioning technology is: Cell ID -> OTDOA -> AGPS -> U-TDOA.
It is a process from rough positioning technology to the positioning technology with high precision.
All positioning technologies can be supplements to each other during the application.
Evolution of UMTS QoS Technology
With the close combination of radio communication technology and IP technology, mobile communication network develops from circuit switching network of GSM to packet switching network of GSM, and to 3G, 3.5G and UMTS that provide high speed real-time data services.
During the whole evolution of mobile network, QoS technology develops to mature to provide satisfactory services according to features of different services.
Analysis on QoS in GSM, GPRS, R99, R4, R5, R6 and R7 tell development of mobile network QoS.
GSM is based on circuit switching mode. It is simple. Connection of circuit can ensure QoS. GSM defines a series of circuit bearer services, including parameters of synchronization/asynchronization, transparent/non-transparent, and limited bit rate set.
They are continuously effective during the evolution of mobile network.
GPRS is based on packet switching mode.
There is no “Connection” concept in GPRS, so QoS assurance of GPRS is more complicated than that of GSM.
QoS parameters that GPRS defines are: Delay level, confidence level, largest data flow, PRI, even data flow and retransmission demand.
QoS parameters can be transmitted between UE and SGSN/GGSN.
QoS of UMTS is to provide end-to-end assurance of services, which is introduced in R99 version, as shown in Figure 3.
End-to-end QoS covers all NEs, including user terminal, access network entity and CN entity. Processing of different interface QoS parameters must be same.
The introduction of QoS layered architecture is a large advancement during the QoS evolution.
Figure 3 QoS Frame of UMTS
Operators decide the bearer mode that UMTS CN adopts.
Its circuit domain can support TDM and ATM bearing modes (in R4 and later version, transmission and control in circuit domain is separated and IP transmission is selective).
Its packet domain supports IP bearer. TDM and ATM bearers both provide QoS assurance.
IP bearer of CN adopts the QoS technology that IETF defines, including integrated service/resource preservation (IntServ/RSVP), Multiple Protocol Label Switching (MPLS), Differential Service (DiffServ), flow project and constraint-based path seek, and so on.
In R99 version, four QoS types are introduced: Conversational, data streaming, interactive and background.
It also defines QoS parameters more than GSM and GPRS. There are new requirements for transmission delay, re transmission mechanism, jitter and code error rate of above four types.
In R4 version, QoS that AAL2 connects on Iub and Iur is optimized, to improve real-time services support.
In addition, QoS negotiation mechanism of radio access bearer is introduced to make use of radio resources more effectively and to enhance the construction capability of radio access bearer.
In R5 version, intercommunication and combination of UE local bearer service, GPRS bearer service and outer bearer service are defined.
They provide QoS assurance for end-to-end services in packet domain.
In UE and GGSN, IP BS Manager may exist.
It usually uses DiffServ and IntServ/RSVP to communicate with outer IP network. IMS, which is QoS policy control mechanism based on services, is also introduced in R5 version.
In R6 version, QoS policy control mechanism based on services is evolved as an independent functional entity, providing services in all packet domains with QoS policy control mechanism based on services.
This mechanism separates control and execution of QoS.
Network administrator can consider the whole network, without paying attention to details, such as, technology and equipment. It reflects the intelligent management of QoS.
In R7 version, amalgamation of UTMS and WLAN is put forward.
Uniform IP QoS is what future UMTS QoS technology will develop to.
Evolution process of QoS is:
QoS parameters do not transmit in the network (GSM) -> QoS parameters transmit between UE and SGSN/GGSN -> Number of QoS parameters increase (GPRS) -> QoS layered architecture, four QoS types, QoS that IETF defines, all NEs that QoS parameters cover, new change in parameters, the number of parameters increase (R99) -> QoS negotiation mechanism of radio access bearer (R4) -> QoS policy control mechanism based on services in IMS (R5) -> QoS policy control mechanism based on services in all packet domain (R6) -> Uniform IP QoS in the amalgamation of UMTS and WLAN (R7 and later version).