Existing Wireless Systems

Advanced Mobile Phone System : It transmits speech signals employing FM, and important control information is transmitted in digital form using FSK. The idea of dividing the entire service area into logical divisions called cells. Each cell is allocated one specific band in the frequency spectrum.

AMPS uses a cell radius of 1 to 16 miles, depending on various factors such as density of users and traffic intensity.

AMPS is that it allows both cell sectoring and splitting. It is also sufficient to have a low-power MS (about 4 watts

or less) and a medium-power BS (about 100 watts). AMPS is capable of supporting about 100,000 customers

per city, and the system is aimed to reduce blocking probability to about 2% during busy hours.

AMPS

Frequency allocation in AMPS is done by dividing the entire frequency spectrum into two bands—Band A and Band B. Frequencies are allocated to these bands

Characteristics of AMPS

Three identification numbers are included in the AMPS system to perform various functions:1. Electronic serial number (ESN): A 32-bit binary number uniquely identifies a cellular unit or a MS and is established by the manufacturer at the factory.2. System identification number (SID): A unique 15-bit binary number assigned to a cellular system. A MS should first transmit this number before any call can be handled. The SID serves as a check and can be used in determining if a particular MS is registered in the same system or if it is just roaming.3. Mobile identification number (MIN): A digital representation of the MS’s 10-digit directory telephone number.

Operation of AMPS

General operation of MS in AMPS

Operation of AMPS

There are two important control channels: 1. forward control channel (FOCC) from the BS to the

MS.2. reverse control channel (RECC) from MS to BS,

both operating at 10 kbps.

And two Voice Channels : Forward voice channel (FVC): FVC is used for one-to-

one communication from the BS to each individual MS.

Reverse voice channel (RVC): Reverse voice channel is used for one-to-one communication from the MS to the BS during calls in progress and is assigned by the BS to a MS for its exclusive use.

When a BS powers up, it has to know its surroundings before providing any service to the MSs.

It scans all the control channels and tunes itself to the strongest channel. Then it sends its system parameters to all the MSs present in its service area. Each MS updates its SID and establishes its paging channels only if its SID matches the one transmitted by the BS. Then the MS goes into the idle state, responding only to the beacon and page signals.

If a call is placed to a MS, the BS locates the MS through the IS-41 message exchanges. Then the BS pages the MS with an order.

If the MS is active, it responds to the page with its MIN, ESN, and so on. The BS then sends the control information necessary for the call, for which the MS has to confirm with a supervisory audio tone (SAT), indicating completion of a call.

If a call is to be placed from a MS, the MS first sends the origination message to the BS on the control channel. The BS passes this to the IS-41 and sends the necessary control signals and orders to the MS. Thereafter, both MS and BS shift to the voice channels. A FVC and RVC control message exchange follows to confirm the channel allocation. Then the actual conversation starts.

General Working of AMPS Phone System

IS-41 is an interim standard that allows handoffs between BSs under control of different MSCs and allows roaming of a MS outside its home system. In order to facilitate this, the following services need to be provided:

Registering of the MS with a visiting MSC. Allowing for call origination in a foreign MSC. Allowing the MS to roam from one foreign system to another. In addition to the three identification numbers described for AMPS, a

switch number (SWNO) is used to identify a particular switch within a group of switches with which it is associated. It is the parameter derived from the concatenation of the SID and switch identification (SWID).

IS-41 functionality is in the application layer to support the mobile application part, the application service element, and the transaction capabilities application part. The association control service element (ACSE) is used to correlate two applications (i.e., setting up an association between the two entities A and B).

ROSE is invoked during the exchange of IS-41 messages using an asymmetric client/server–based model in which a client requests a service and the server responds with an appropriate reply.

IS-41

Relationship between IS-41 and OSI protocol stack

Internetworking of IS-41 and AMPS

The various operations supported by IS-41 are as follows: Registration in a new MSC: When a mobile terminal moves into a new area

(served by a different MSC), it has to register with the new serving MSC. Calling an idle MS in a new system: When a call is to be routed to a MS in a

new system, the HLR of the home MSC contacts the VLR of the latest visiting system and, after appropriate authentication and exchange of IS-41 messages, allows the call to be routed to the MS in the visiting system.

Call with unconditional call forwarding: In case the visiting MS has unconditional call forwarding in effect, the visiting MSC sends a location request response to the home MSC, which contains the identifier of the telephone to which this call is to be forwarded.

Call with no answer: In case the visiting MS does not answer the call, the calling terminal is issued an appropriate response and the call is disconnected.

Calling a busy MS: This follows the same pattern as for call with no answer, except that a busy tone is conveyed to the calling terminal in case the MS does not have call waiting. If the MS has call waiting, the MS is informed of the second incoming call.

Handoff measurement request: A serving MSC can sometimes request an adjacent MSC for a handoff measurement.

Recovery from failure at the HLR: This IS-41 procedure is used in the event of an HLR failure. In case of failure the HLR sends an UNRELDIR (Unreliable Roamer Data Directive INVOKE) to all the VLRs in its database.

Support Operations

GSM (Global System for Mobile communications or Groupe Speciale Mobile). The main objective of GSM is to remove any incompatibility among the systems by allowing the roaming phenomenon for any cell phone.

Specific functions of different constituents are as follows: Base station controller (BSC): The main function of the BSC is

to look over a certain number of BTSs to ensure proper operation. It takes care of handoff from one BTS to the other, maintains appropriate power levels of the signal, and administers frequency among BTSs.

Mobile switching center (MSC): The MSC basically performs the switching functions of the system by controlling calls to and from other telephone and data systems.

Authentication center (AUC): AUC unit provides authentication and encryption parameters that verify the user’s identity and ensure the confidentiality of each call.

Equipment identity register (EIR): EIR is a database that contains information about the identity of mobile equipment that prevents calls from being stolen and prevents unauthorized or defective MSs.

GSM

GSM has been allocated an operational frequency from 890MHz to 960 MHz to reduce possible interference, the MS and the BS use different frequency ranges.

GSM follows FDMA and allows up to 124 MSs to be serviced at the same time. The frequency band of 25MHz is divided into 124 frequency division multiplexing (FDM) channels, each of 200 kHz, and a guard frame of 8.25 bits is used in between any two frames transmitted either by the BS or the MS.

GSM uses a variety of multiplexing techniques to create a collection of logical channels.

Frequency Bands and Channels

The GSM system uses a variety of control channels to ensure uninterrupted communication between MSs and the BS. Three control channels are used for broadcasting some information to all MSs:

1. Broadcast control channel (BCCH): Used for transmitting system parameters, (e.g., the frequency of operation in the cell, operator identifiers) to all the MSs.

2. Frequency correction channel (FCCH): Used for transmission of frequency references and frequency correction burst of 148 bits length.

3. Synchronization channel (SCH): Used to provide the synchronization training sequences burst of 64 bits length to the MSs.

Three common control channels are used for establishing links between the MS and the BS, as well as for any ongoing call management:

1. Random-access channel (RACH): Used by the MS to transmit information regarding the requested dedicated channel from GSM.

2. Paging channel: Used by the BS to communicate with individual MS in the cell.

3. Access-grant channel: Used by the BS to send information about timing and synchronization.

Channels in GSM

Channels in GSM

Two dedicated control channels are used along with traffic channels to serve for any control information transmission during actual communication:

Slow associated control channel (SACCH): Allocated along with a user channel, for transmission of control information during the actual transmission.

Stand-alone dedicated control channel (SDCCH): Allocated with SACCH; used for transfer of signaling information between the BS and the MS.

Fast associated control channel (FACCH): FACCH is not a dedicated channel but carries the same information as SDCCH.

Frames in GSM

Frame structure in TDMA.

Several identity numbers are associated with a GSM system, as follows:

International mobile subscriber identity (IMSI).

Subscriber identity module (SIM): Every time the MS has to communicate with a BS, it must correctly identify itself. A MS does this by storing the phone number, personal identification number for the station, authentication parameters, and so on in the SIM card. Smart SIM cards also have a flash memory that can be used to store small messages sent to the unit. The main advantage of SIM is that it supports roaming with or without a cell phone, also called SIM roaming.

Mobile system ISDN (MSISDN).

Identity Numbers Used by a GSM System

Location area identity (LAI). International MS equipment identity (IMSEI).

MS roaming number (MSRN).

Temporary mobile subscriber identity (TMSI): As all transmission is sent through the air interface, there is a constant threat to the security of information sent. A temporary identity is usually sent in place of IMSEI.

Identity Numbers Used by a GSM System

Interfaces, Planes, and Layers of GSM

Authentication processin GSM

Functional planes in GSM.

Handoff in GSM is divided into four major categories: Intracell/intra-BTS handoff: The channel for the connection is

changed within the cell (usually when higher interference occurs). Intercell/intra-BSC handoff: In this case, the change is in the

radio channel between two cells that are served by the same BSC. Inter-BSC/intra-MSC handoff: A connection is changed between

two cells that are served by different BSCs but operate in the same MSC.

Inter-MSC handoff: A connection is changed between two cells that are in different MSCs.

Basic handoff: When the MS travels from its home MSC to a foreign MSC.

Subsequent handoff: When the MS travels from one foreign MSC to another foreign MSC

Handoff

Inter-MSC handoff

The short message service (SMS) is the ability to send or receive a text message to or from mobile phones.

The GSM system supports SMS messages using unused bandwidth and has several unique features. SMS features confirmation of message delivery.

SMS can be sent and received simultaneously with GSM voice, data, and fax calls.

SMS text is not sent directly from a sender to the receiver but is always processed via a SMS center instead.

A single SMS can be up to 160 characters of text in length, and these 160 characters comprise a combination of words, numbers, or alphanumeric characters.

Non-text–based SMSs (for example, in binary format) are also supported.

There are ways of sending multiple SMS. For example, SMSs concatenation (stringing several short messages together) and SMS compression (getting more than 160 characters of information within a single short message) have been defined and incorporated in the GSM SMS standards

Short Message Service (SMS)

PCS (personal communications services) employs an inexpensive, lightweight, and portable handset to communicate with a PCS BS.

PCS encompasses the whole spectrum of communication services ranging from an ordinary cellular telephone to cable television.

The PCS can be classified into high-tier and low-tier standards. High-tier systems include high-mobility units with large batteries, such as a MS in a car.

Low-tier systems include systems with low mobility, capable of providing high-quality portable communication service over a wide area. The PCS low-tier standards based on personal access communications systems (PACS) and digital European cordless telecommunications (DECT) .

PCS

FCC view of PCS

Chronology of PCS Development

CT2 (Cordless Telephone) operates using FDMA with a speech rate of 32 kbps using adaptive differential pulse code modulation (ADPCM). The transmitter data rate is 72 kbps. CT2 uses TDD, which allows BS and MS to share one channel.

DECT (Digital European Cordless Telecommunications) standard is a second generation cordless telephone system. DECT operates on frequencies ranging from 1880MHz to 1900MHz and uses ADPCM with 32 kbps speech rate.

CT2 TDD slot (first generation)

DECT TDD slot(second-generation)

The Bellcore view of PCS is based on five different access services provided between the Bellcore client company (BCC), the BCC network, and the PCS wireless provider network as follows:1. PCS access service for networks (PASN) is a connection service to

and from the PCS service provider (PSP).2. PCS access service for controllers (PASC) is a service for use with

PCS wireless provider (PWP) across radio channels and some type of automatic link transfer capability.

3. PCS access service for ports (PASP) is an interface into PWP.4. PCS service for data (PASD) is a database information transport

service.5. PCS access service for external service providers (PASE) is used to

support specialized PCS services like voice mail, paging, and so on. Bellcore PCS Reference Architecture: The air interface A

connects the MS with the radio port (RP) which is used among other things to convert the air interface to or from a wire or fiber signal. The RPs are connected through the port (P) interface to the radio port control unit (RPCU).

Bellcore View of PCS

Description of the PCS Air Interface : PCS uses TDMA for channel access. The reverse frame format for PCS, with a duration of 2.5 ms, Eight frames are multiplexed together to create a superframe 20 ms in duration. The downlink slot duration is 312.5 μs, and eight such slots are present in a frame to give a frame of 2.5 ms. The superframe consists of eight such frames for a total duration of 20 ms, which is similar to the uplink superframe. 15 bits CRC (cycle redundancy check) is calculated from slow and fast channels for each burst. Also, a 1 bit PCC (power control channel) is set according to individual systems.

Bellcore PCS architecture

Forward TDMA frame for PCS

IS-95 uses the existing 12.5MHz cellular bands to derive 10 different CDMA bands (1.25MHz per band). Because the same frequency can be used even in adjacent cells, the frequency reuse factor is 1. The channel rate is 1.228 Mbps (in chips per second).

RAKE receivers are used to combine the output of several received signals. Sixty-four-bit orthogonal Walsh codes (W0 to W63) are used to provide 64

channels in each frequency band. In addition to Walsh codes, long pseudo noise (PN) codes and short PN codes are also used.

The logical channels of CDMA are the control and traffic channels. The control channels are the pilot channel (forward), the paging channels

(forward), the sync channels (forward), and the access channels (reverse). The traffic channels are used to carry user information between the BS and

the MS, along with signaling traffic. Four different rates are used. When the user speech is replaced by the associated signal, it is called

blank and burst. When part of the speech is replaced by signaling information, it is called dim and burst. The downlink or forward link has a power control sub-channel that allows the mobile to adjust its transmitted power by ±1 dB every 1.25 ms. The pilot channelW0 is always required.

There can be one sync channel and seven paging channels; the remaining fifty-six channels are called traffic channels.

IS-95

Pilot channel: The pilot channel is used by the base station as a reference for all MSs. It does not carry any information and is used for strength comparisons and to lock onto other channels on the same RF carrier. The signals (pilot, sync, paging, and traffic) are spread using high frequency spread signals I and Q using modulo 2 addition. This spread signal is then modulated over a high frequency carrier and sent to the receiver, where the entire process is inverted to get back the original signal.

Sync channel: The sync channel is an encoded, interleaved, and modulated spread-spectrum signal that is used with the pilot channel to acquire initial time synchronization. It is assigned the Walsh code W32.

Paging channel: As the name suggests, the paging channel is used to transmit control information to the MS. When the MS is to receive a call, it will receive a page from the BS on an assigned paging channel. There is no power control for the paging channel on a per-frame basis. The paging channel provides the MSs system information and instructions.

IS-95

Logical channels in IS-95.

Pilot and sync channels in IS-95

Access channel: The access channel is used by the MS to transmit control information to the BS. The access rate is fixed at 4800 bps. All MSs accessing a system share the same frequency. When any MS places a call, it uses the access channel to inform the BS. This channel is also used to respond to a page.

Forward traffic channels: Forward traffic channels are grouped into rate sets. Rate set 1 has four elements: 9600, 4800, 2400, and 1200 bps. Rate set 2 has four elements: 14,400, 7200, 3600, and 1800 bps. Walsh codes that can be assigned to forward traffic channels are available at a cell or sector (W2 through W31, and W33 through W63). Only 55 Walsh codes are available for forward traffic channels. The speech is encoded using a variable-rate encoder to generate forward traffic data depending on voice activity. The power control sub-channel is continuously transmitted on the forward traffic channel.

Reverse traffic channels: For rate set 1, the reverse traffic channel uses 9600, 4800, 2400, or 1200 data rates for transmission. The duty cycle for transmission varies proportionally with the data rate being 100% at 9600 bps to 12.5% at 1200 bps. The reverse traffic channel processing is similar to the access channel except for the fact that the reverse channel uses a data burst randomizer.

IS-95

Paging channel generation in IS-95

Access channel generation in IS-95

Rate set 1 forward traffic channel generation in IS-95

Rate set 2 forward traffic channel generation in IS-95

Forward/reverse trafficchannel frame structurefor rate set 1.

Forward/reverse trafficchannel frame structurefor rate set 2.

Rate set 1 reversetraffic generation

Rate set 2 reversetraffic generation

Power Control

Power control plays an important role in view of the fact that every receiver gets the signals transmitted by all the transmitters. To ensure maximum efficiency, the power received at the BS from all the MSs must be nearly equal.

If the received power is too low, there is a high probability of bit errors, and if the received power is too high, interference increases. Power control is applied at both the MSs as well as the BS.

There are several different mechanisms that are used for power control initiated either by the MS or the BS, and the control can be based on the signal strength perceived by the BS or can depend on other parameters.

In open-loop power control at the MS, the MS senses the strength of the pilot signal and can adjust its power based on that. If the signal is very strong, it can be assumed that the MS is too close to the BS and the power level should be dropped.

In closed-loop power control at the MS, power control information is sent to the MSs from the BS. This message indicates either a transition up or transition down in power.

In open-loop power control at the BS, the BS decreases its power level gradually and waits to hear the frame error rate (FER) from the MS. If the FER is high, it increases its power level.

The International Telecommunications Union-Radio communications (ITU-R) developed the 3G specifications to facilitate a global wireless infrastructure, encompassing terrestrial and satellite systems providing fixed and mobile access for public and private networks.

The key features of the IMT-2000 system are as follows:1. High degree of commonality of design worldwide.2. Compatibility of services within IMT-2000 and with fixed

networks.3. High quality.4. Small terminal for worldwide use, including pico, micro,

macro, and global satellite cells.5. Worldwide roaming capability. 6. Capability for multimedia applications and a wide range of

services and terminals.

IMT-2000

In 1992 the World Administration Radio Conference (WARC) specified the spectrum for the 3G mobile radio system.

Europe and Japan followed the FDD specification. The lower-band parts of the spectrum are currently used for DECT and PHS (Personal Handyphone System), respectively. The FCC in the United States has allocated a significant part of the spectrum in the lower band to 2G PCS systems. Most of the North American countries are following the FCC frequency allocation. Currently no common spectrum is available for 3G systems worldwide.

International Spectrum Allocation

The following services are provided by third-generation cellular systems: High bearer rate capabilities, including– 2 Mbps for fixed environment– 384 kbps for indoor/outdoor and pedestrian environment– 144 kbps for vehicular environment Standardization work– Europe (ETSI: European Telecommunications Standardization Institute) ⇒UMTS (W-CDMA)– Japan (ARIB: Association of Radio Industries and Businesses) ⇒ W-CDMA– USA (TIA: Telecommunications Industry Association) ⇒ cdma2000 Scheduled service – Service started in October 2001 (Japan’s W-CDMA)

Services Provided by Third-Generation Cellular Systems

A harmonized 3G system based on the Operators Harmonization Group (OHG) recommendation is required to support the following:

High-speed data services, including Internet and intranet applications. Voice and non-voice applications. Global roaming. Evolution from the embedded base of 2G systems. ANSI-41 (American National Standards Institute-41) and GSM-MAP core networks. Regional spectrum needs. Minimization of mobile equipment and infrastructure cost. Minimization of the impact of intellectual property rights (IPRs). The free flow of IPRs. Customer requirements on time.

Harmonized 3G Systems

The multimedia messaging service (MMS) is an open industry specification developed by the WAP forum for the 3rd Generation Partnership Program (3GPP).

MMS has been designed to allow rich text, color, icons and logos, sound clips, photographs, animated graphics, and video clips and works over the broadband wireless channels in 2.5G and 3G networks. MMS and SMS are similar in the sense that both are store-and-forward services where the message is first sent to the network which then delivers it to the final destination.

MMS service can be used to send messages to a phone or may be delivered as an email.

The main components of MMS architecture are: MMS Relay—Transcodes and delivers messages to mobile subscribers. MMS Server—Provides the “store” in the store-and-forward MMS

architecture. MMS User Agent—An application server gives users the ability to view,

create, send, edit, delete, and manage their multimedia messages. MMS User Databases—Contain records of user profiles, subscription

data, etc.

Multimedia Messaging Service (MMS)

The content of MMS messages is defined by the MMS conformance specification version 2.0.0, which specifies SMIL 2.0 (synchronization multimedia integration language) basic profile for the format and the layout of the presentation.

Although MMS is targeted toward 3G networks, carriers all over the world have been deploying MMS on networks like 2.5G using WAP, and it helps in generating revenue from existing older networks.

Some of the possible application scenarios are as follows: Next-generation voicemail—Makes it possible to leave text, pictures,

and even video mail. Immediate messaging—MMS features “push” capability that enables

the message to be delivered instantly if the receiving terminal is on and avoids the need for “collection” from the server.

With MMS, users have an unprecedented range of choices about how their mail is to be managed. They can predetermine what categories of messages are to be delivered instantly, stored for later collection, redirected to their PCs, or deleted.

Mobile fax—Using any fax machine to print out any MMS message. Sending multimedia postcards.

(MMS)

Network Reference Architecture :

Universal Mobile Telecommunications System (UMTS)

UMTS Release’99 architecture inherits a lot from the global system for mobile (GSM) model on the core network (CN) side. The MSC basically has very similar functions both in GSM and UMTS. Instead of circuit-switched services for packet data, a new packet node, packet data access node (PDAN), or 3G serving general packet radio services (GPRS) support node (SGSN) is introduced.

The major changes in the new architecture are in the radio access network (RAN), which is also called UMTS terrestrial RAN(UTRAN).

There is a totally new interface called Iur, which connects two neighboring radio network controllers (RNCs).

This interface is used for combining macro diversity, which is a new WCDMA-based function implemented in the RNC.

In 2G, the RAN is separated from the CN by an open interface, called “A” in circuit-switched (CS) and Gb in packet-switched (PS) networks.

In 3G, the corresponding interfaces are called Iu Cs and IuPs. The circuit-switched interface will utilize ATM, while the packet-switched interface will be based on IP.

Universal Mobile Telecommunications System (UMTS)

UTRAN Architecture : UTRAN consists of a set of radio network subsystems (RNSs).

The RNS has two main elements: Node B and a RNC. The RNS is responsible for the radio resources and transmission/reception in a set of cells. A RNC is responsible for the use of and allocation of all radio resources of the RNS to which it belongs. The responsibilities of the RNC include :

Intra-UTRAN handoff. Macro diversity combining and splitting of the Iub DataStream's. Frame synchronization. Radio resource management. Outer loop power control. Serving RNS relocation. UMTS radio link control (RLC) sub-layers function execution.

Universal Mobile Telecommunications System (UMTS)

UTRAN Logical Interfaces: In UTRAN, the protocol structure is designed so that the layers and planes are logically independent of each other and, if required, parts of protocol structure can be changed in the future without affecting other parts.

The protocol structure contains two layers: the radio network layer (RNL) and the transport network layer (TNL).

A general protocol model for UTRAN interfaces is RANAP (radio access network application protocol).

Channels : Three types of channels are defined in UMTS: Transport channels are described by how the information is

transmitted on the radio interface. the services offered by the physical layer to the higher layers. A general classification of transport channels is into two groups:

1. Common transport channels (where there is a need for in-band identification

of the UEs when particular UEs are addressed) 2. Dedicated transport channels (where the UEs are identified by

the physical channel, i.e., code, time slot, and frequency)

Universal Mobile Telecommunications System (UMTS)

Common transport channel types:– Random access channel (RACH): A contention-based uplink channel used for transmission of relatively small amounts of data (e.g., for initial access or non–real-time dedicated control or traffic data).– ODMA (Opportunity driven multiple access) random access channel (ORACH): A contention-based channel used in relay link.– Common packet channel (CPCH): A contention-based channel used for transmission of bursty data traffic.– Forward access channel (FACH): Common downlink channel without closed-loop power control used for transmission of relatively small amount of data.– Downlink shared channel (DSCH): A downlink channel shared by severalUEs carrying dedicated control or traffic data.– Uplink shared channel (USCH): An uplink channel shared by several UEscarrying dedicated control or traffic data, used in TDD mode only.– Broadcast channel (BCH): A downlink channel used for broadcast ofsystem information into an entire cell.– Paging channel (PCH): A downlink channel used for broadcast of controlinformation into an entire cell allowing efficient UE sleep modeprocedures.

Channels

Dedicated transport channel types:– Dedicated channel (DCH): A channel dedicated to one UE used in uplink or downlink.– Fast uplink signaling channel (FAUSCH): An uplink channel used to allocate dedicated channels in conjunction with FACH.– ODMA dedicated channel (ODCH): A channel dedicated to one UE used in relay link.

Logical channels are described by the type of information they carry. Two types of logical channels are defined: traffic and control channels. Traffic channels (TCH) are used to transfer user and/or signaling data. Signaling data consists of control information related to the process of a call. Control channels carry synchronization and information related to the radio transmission.

Channels

Control channels:– Broadcast control channel (BCCH): A downlink channel for broadcasting system control information.– Paging control channel (PCCH): A downlink channel that transfers paging information. This channel is used when the network does not know the location cell of the UE, or the UE is in the cell-connected state (utilizing UE sleep mode procedures).– Common control channel (CCCH): Bidirectional channel for transmitting control information between network and UEs. This channel is common used by the UEs having no RRC connection with the network and by the UEs using common transport channels when accessing a new cell after cell reselection.– Dedicated control channel (DCCH): A point-to-point bidirectional channel that transmits dedicated control information between a UE and the network. This channel is established through the RRC connection setup procedure.– Shared channel control channel (SHCCH): Bidirectional channel that transmits control information for uplink and downlink shared channels between the network and UEs. This channel is for TDD only.– ODMA common control channel (OCCCH): Bidirectional channel for transmitting control information between UEs.– ODMA dedicated control channel (ODCCH): A point-to-point bidirectional channel that transmits dedicated control information between UEs. This channel is established through the RRC connection setup procedure.

Channels

Traffic channels: – Dedicated traffic channel (DTCH): A DTCH is a point-to-point

channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both uplink and downlink.

– ODMA dedicated traffic channel (ODTCH): An ODTCH is a point-to point channel, dedicated to one UE, for the transfer of user information between UEs. An ODTCH exists in relay link.

– Common traffic channel (CTCH): A point-to-multipoint unidirectional channel for transfer of dedicated user information for all or a group of specified UEs.

Physical channels are defined differently for FDD and TDD. All physical channels follow four-layer structure of superframe,

radio frames, sub frames, and time slots/codes. Depending on the resource allocation scheme, the configurations of sub frames or time slots are different. All physical channels need guard symbols in every time slot. The time slots or codes are used as a TDMA component so as to separate different user signals in the time and the code domain.

Channels

Logical channels in UTRAN