E1 Link

EVOLVING MOBILE NETWORKS UMTS

2009-06-15T03:25:00.000-07:00

EVOLVING MOBILE NETWORKS
While the history of mobile communications is long [1–3], and the background of mo
bile networks therebyx is also long, in this chapter we focus on the historic evolution in
terms of network architecture and services starting with 2nd generation (2G) mobile
systems. In particular we consider the development of the architecture of Global Systems
for Mobile Communications (GSM), since it is by far the most widespread mobile
system in the world today. This will provide the basis to cover the introduction of Universal
Mobile Telecommunication Services (UMTS) in relation to its Core Network
(CN) and radio architectures. The latter will in turn serve as the platform to present
UMTS Radio Access Technology, which is one the aims of this book.
1.1 THE GROWTH OF MOBILE COMMUNICATIONS
Today wireless voice service is one of the most convenient and flexible means of modern
communications. GSM technology has been at the leading edge of this wireless
revolution. It is the technology of choice in over 120 countries and for more than 200
operators worldwide. Current estimates are that by the year 2001 there will be around
600 million wireless subscribers (e.g. mobile telephone users), out of which more than
50% will depend on GSM technology.
As the wireless revolution has been unfolding, the Internet has also shown a phenomenal
growth simultaneously. The advent of the World Wide Web and web browsers has
propelled TCP/IP protocols into the main stream, and the Internet is widespread not
only in the corporate environment but also in households. Large number of consumers
have embraced the Internet and use it today to access information online, for interactive
business transactions, and e-commerce as well as electronic mail. Figure 1.1 illustrates
the growth in mobile and Internet subscribers.
The success of mobile communications, i.e. the ubiquitous presence it has established
and the emergence of the Internet point towards a tremendous opportunity to offer integrated
services through a wireless network.
One of the main market segments for wireless services besides corporate intranet/
internet access is the consumer sector. The availability of intelligent terminals1 or
multipurpose wireless telephones is already ushering a new era of the information age,
where subscribers can receive directly through GSM-SMS: news, sport updates, stock
quotes, etc. However, the progress of audiovisual techniques and the support for a Weblike
interface in a new generation of terminals, will push consumers to a new era of
multimedia communications with a focus on services rather than technology.
To support the growth of Internet type services2 and future demands for wireless services,
ETSI SMG and other standards bodies3 have completed or are now completing
specifications to provide a transition platform or evolution path for wireless networks
like GSM. Figure 1.2 illustrates the wireless data technology options.
The technology options in Figure 1.2 can be summarized as follows:
14.4 kbits/s allows GSM data calls with a rate of 14.4 kbits/s per time slot, resulting
in a 50% higher data throughput compared to the current maximum speed of 9.6
kbits/s.
High Speed Circuit Switched Data (HSCSD) aggregates symmetrically or asymmetrically
several circuit channels, e.g. 28.8 kbits/s for two time slots (2 + 2) or
43.2 kbits/s for three time slots (3 + 1).
General Packet Radio Service (GPRS) enables GSM with Internet access at high
spectrum efficiency by sharing time slots between different users. It affords data
rates of over 100 kbits/s to a single user while offering direct IP connectivity.
Enhanced Data Rate for GSM Evolution (EDGE) modifies the radio link modulation
scheme from GMSK to 8QPSK. Thereby increasing by three times the GSM
throughput using the same bandwidth. EDGE in combination with GPRS (EGPRS)
will deliver single user data rates of over 300 kbits/s.
UMTS as 3rd generation wireless technology utilizes a Wideband CDMA or
TD/CDMA transceiver. Starting with channel bandwidths of 5 MHz it will offer
data rates up to 2 Mbits/s. UMTS will use new spectrum and new radio network
configurations while using the GSM core infrastructure.

E1 Link for ATM Physical Interface

2008-10-20T22:46:00.000-07:00

E1 ATM Physical Interface

For information on testing E1 links

The E1 interface operates at 2 Mbps over coax cables, compliant with ATM Forum UNI specifications. It supports both PLCP and direct cell mapping and complies with the following standards: G.704, G.706, G.732. The interface has BNC connectors.

The E1 transmission link consists of 32 transmission channels (0-31), each of which is 64 Kbits/sec. The overall transmission rate is 2.048 Mbits/sec. Channels 0 and 16 are reserved for transmission management, while all other channels are used for payload. The payload bandwidth is thus 1.920 Mbits/sec. Since ATM uses 48 out of the possible 53 bytes for payload transmission, the net transmission rate becomes 1.738 Mbits/sec.

Channel 0 carries F3-OAM information, signals loss of frame or synchronization, and is responsible for transferring FERF and LOC messages. Channel 16 is reserved for signalling.

Direct Mapping

The direct mapping of ATM cells onto E1 transmission frames is specified in CCITT recommendation G.804. This specifies that ATM cells are to be carried in bits 9-28 and 137-256 (corresponding to channels 1-15 and 17-31).

The following is an illustration of the E1 frame format when direct mapping of ATM cells is used. The 53 byte ATM cell begins with a header and wraps around consecutive E1 frames.

PLCP Cell Mapping

The PLCP format for E1 is described in ETSI document ETS 300 213, where an E1 PLCP frame is specified as consisting of ten rows of 57 bytes each. Four bytes are added to the cell length of 53 bytes to provide the various overhead functions.

The E1 frame structure with PLCP cell mapping is illustrated in the following diagram:

A-bits
Separator bytes.

P-bits
Path overhead identifier.

C1
Pad bit counter.

M-bits
SIP layer 1 management information.

G1
PLCP path status.

B1
Bit-interleaved parity 8 (BIP-8).

F1
PLCP path user channel.

Z-bits
For future use.

Thirty of the available 32 E1 channels are used for transporting the PLCP frame. The remaining two channels are reserved for E1 framing and signalling functions. The PLCP frame is octet aligned to the channel boundaries in the E1 frame; thus the A1 octet of the first row of the PLCP frame is inserted into time slot 1 of the E1 frame.

General Packet Radio Service (GPRS)

2008-09-09T22:41:00.000-07:00

General Packet Radio Service
General Packet Radio Service (GPRS) is a standard designed by ETSI for GSM, DCS, PCS digital cellular networks to enable high-speed wireless Internet and other data communications. Sometimes, it is referred to as the 2.5 generation (2.5G) technology. GPRS can support applications based on standard data protocols, and interworking with IP and X.25 networks.

GPRS uses a packet-mode technique to transfer high-speed and low-speed data and signalling in an efficient manner over GSM radio networks. GPRS data speeds are expected to reach theoretical data speeds of up to 171.2 Kbps. By implementing GPRS, the following objectives can be met:

give support for bursty traffic
use efficiently network and radio resources
provide flexible services at relatively low costs
possibility for connectivity to the Internet
provide fast access time
to have and support flexible co-existence with GSM voice
GPRS architecture consists of Gateway GPRS Support Node (GGSN) and a Serving GPRS Support Node (SGSN). The GGSN acts as the gateway to other packet data networks such as the Internet. The SGSN is the serving node that enables virtual connections to the GPRS enabled mobile device and delivery of data. GGSN provides interworking with external packet-switched networks, and is connected with SGSNs via an IP-based GPRS backbone network.

GPRS security functionality is equivalent to the existing GSM security. The SGSN performs authentication and cipher setting procedures based on the same algorithms, keys, and criteria as in existing GSM. GPRS uses a ciphering algorithm optimized for packet data transmission.

GPRS Network Architecture

GPRS: General Packet Radio Service

G.732-G.704 Framing Stardard

2007-09-02T21:59:00.000-07:00

The International CCITT framing format is adopted by most countries (Europe, Central/South America, etc.). These facilities operate at 2.048 MBPS.

This framing format is actually defined in CCITT Recommendation G.704, although Recommendation G.732 supplements G.704.

G.704: Synchronous Frame Structures
Used and Primary and Secondary
Hierarchical Levels

G.732: Characteristics of Primary PCM
Multiplex Equipment Operating at
2048 KBPS.

G.732-G.704 Framing Stardard
The standard frame is 32 timeslots, with each timeslot consisting of an 8-bit byte. A Multiframe consists of 16 frames, numbered zero to fifteen.

The timeslots are numbered 0 to 31. Timeslot 0 is used for:

- Synchronization
- Alarm Transport
- International Carrier use

Timeslot 16 may be used to transmit Channel Associated Signaling (CAS) information. Note that G.732 DOES NOT define the signaling states, only the transport of the states through the G.732 frame.

However, G.704 recognizes the requirement for Common Channel Signaling and also allows the TRANSPARENT End-To-End transport of Timeslot 16.

G.703

E1 for business

2007-08-29T03:39:00.000-07:00

Business E1 is the voice-call service offered to customers with the competitive tariff that can help them reduce their cost especially for calls from fixed-lines to mobiles.

It is required that customers have to have PABX with PRI-E1 (Q.931 standard) interface in order to make interconnection with True move network where GMSC is the point of interconnection.

In the delivered solution, The operator is responsible for transmission providing between customer’ s PABX and GMSC whereby its cost will be charged on operator side. Operator is responsible for PRI-E1 configuring in GMSC in order to provide the proper voice-call service as well as charging and billing for customers’ usage.

What is E1
G.703
E1 Standard

E1 Frame Structure

E1 Physicals

2007-08-28T22:57:00.000-07:00

E1 Physicals

Rate of 2.048 mbps
Single frame is 256 bits wide (125 microseconds)
32 timeslots (DS0 s)
- Each DSO is 8 bits wide (64K rate per second)
Timeslot 0 used for Synchronization

Two types of physical delivery
Unbalance 120 W
- Copper delivery on 4 wires
one pair for RX (1+2)
one pair for TX (4+5)
Balanced 75 W
- Coax with BNC connectors
one cable for RX
one cable for TX

2007-08-28T22:56:00.001-07:00

E1 standard (2)
The standard frame is 32 timeslots, with each timeslot consisting of an 8-
bit byte. A MultiFrame consists of 16 frames, numbered 0 to 15.

The timeslots are numbered 0 to 31. Timeslot 0 is used for:
- Synchronization
- Alarm Transport
- International Carrier use

Timeslot 16 may be used to transmit Channel Associated Signaling (CAS)
- information. Note that G.732 DOES NOT define the signaling states, only
- The transport of the states through the G.732 frame.

However, G.704 recognizes the requirement for Common Channel
Signaling and also allows the TRANSPARENT End-To-End transport of
Timeslot 16.

E1 Standards

2007-08-28T22:55:00.000-07:00

E1 standard (1)

The International CCITT framing format is adopted by most countries (Europe, Central/South America, etc.). These facilities operate at 2.048 MBPS.

This framing format is actually defined in CCITT
Recommendation G.704, although Recommendation G.732 supplements G.704.

G.704: Synchronous Frame Structure
- Used and Primary and Secondary
- Hierarchical Levels

G.732: Characteristics of Primary PCM
- Multiplex Equipment Operating at
- 2048 KBPS.

TS-16 in E1 Multi Frame Structuret

2007-08-28T22:44:00.001-07:00

TS-16 in E1 Multi Frame Structuret
- Common Channel Signaling (CCS) ? at least one channel (usually TS16) is used for

signaling and serves asynchronously all the channels
- Channel Associated Signaling (CAS) ? in each multi-frame, for each channel, there is a

frame that half of it?s TS16, is dedicated for that channel signaling:
- Frame 0 is used for alarm indication and spare bits
- Frame 1 is used for channels 1 and 16 (4 bits each)
- Frame 2 is used for channels 2 and 17 (4 bits each)
- ?
- Frame 15 is used for channels 15 and 30 (4 bits each)

- When the bits aren?t used for signaling 2nd and 4th bits should be ?1? and the 3rd

should be ?0?.
- The bits can be used for signaling of 2 states (1 bit), 4 states (2 bits) or 15 states

(4 bits minus ?0000?).
- This was used mainly to the on-off-keying slow dial method (OOK). Today DTMF is used

in each data channel as part of the data

E1 Multi Frame Structure

2007-08-28T22:43:00.000-07:00

E1 Multi Frame Structure
- A multi-frame is formed from consecutive 16 frames numbered 0-15
- It is used for adding information regarding the data:
- In TS0 ? synchronization between frames & Error Correcting
- In TS16 ? Signaling

TS-0 in E1 Multi Frame Structure
- Synchronization is gained in every 2nd frame. The synchronization pattern is 0011011.
Specifically in the even numbered frames (0, 2?) bits 1-7 (from 0-7) holds the mentioned

pattern.
- Note that this synchronization does not involves a clock, but bits are transmitted

constantly even when the line is idle.
- Error correcting (optional) is done using a Cyclic Redundancy Check (CRC-4) that uses

4 bits for every half multi-frame (8 frames). specifically the 4 bits are placed in bit

0 of every 2nd (even) frame, before the synchronization pattern.
- Error indication bits using CRC-4 are held in frames 13 and 15
- Remote alarm indication bit is held in bit 3 of odd numbered frames (1, 3?)
- Other bits in the odd frames are spare bits.

E1 Frame Structuret

2007-08-28T22:42:00.001-07:00

E1 Frame Structuret- A Frame is composed from 256 bits that are divided to 32 Time Slots (TS) x 8 bits per

TS - Each channel rate is 64 Kb/s
- The channels are in consecutive time slots numbered 0-31
- Frame rate is 8 KHz
- TS 1-15, 17-31 are used for user data and are referred as channels 1-30
- TS0 is used for synchronization, alarms and messages (future use)
- TS16 is used for signaling (but can be also used for data)

E1 bit Structure

2007-08-28T22:40:00.000-07:00

E1 bit Structure
There are several E1 modes, all use 2048 Kb/s:
- Unframed (UNF) - stream of 2048 Kb/s with no channel association
- Framed (FR) ? all 32 slots are used for data, detection of boundaries is gained with

TS0 - Multi-Framed (MF) ? TS0 is used for synchronization, all other channels are unaffected
- MF + Channel Associated Signaling (CAS)1
- MF + Cyclic Redundancy Check (CRC)
- MF + Common Channel Signaling (CCS)/CAS + CRC1

G.703

2007-08-28T19:19:00.000-07:00

G.703 is a CCITT standard for transmitting voice over digital carriers such as T1 and E1. G.703 provides the specifications for pulse code modulation (PCM) at data rates from 64 Kbps to 2.048 Mbps. G.703 service is typically used for interconnecting data communications equipment such as bridges, routers, and multiplexers. G.703 is transported over balanced (120 ohm twisted pair) or unbalanced (dual 75 ohm coax) cable. Whether the G.703 is balanced or unbalanced depends on your geographic location and the carrier that supplies the service. Balanced service is the most common around the world with the exception of the U.K. and the Netherlands. However, the new Open Network Provision standard of the EEC requires that balanced service be available throughout all of Europe.

At data rates of 64 kbps over balanced wire, there are three ways of transmission: co-directional, central directional, and contra-directional. Co-directional uses four twisted wires, two to transmit and two to receive. The data and timing are sent in the same direction over the same wires. Central directional is rarely used. Here the clock signals are supplied on different wires from a centralized clock such as an atomic clock. Central directional can use six or eight wires to send a clock signal in both directions or in separate directions. The six-wire version uses two for the clock signals and four for the data signals, and the eight-wire version uses four for clock signals and the other four for data. The contra-directional is an eight-wire version that uses two wires each for transmitting and receiving and two pairs for the clock signals. (Clock signals originate at the Data Communications Equipment (DCE) and are sent to the Data Terminal Equipment (DTE).

CONTRIBUTORS: Hugh Parker
LAST UPDATED: 30 Nov 2002

High bit rate Digital Subscriber Line

2007-08-27T03:08:00.000-07:00

High bit rate Digital Subscriber Line (HDSL) was the first DSL technology that uses a higher frequency spectrum of copper, twisted pair cables. HDSL was developed in the USA, as a better technology for high-speed, synchronous circuits typically used to interconnect local exchange carrier systems, and also to carry high-speed corporate data links and voice channels, using T1 lines.
T1 circuits operate at 1.544 Mbit/s. These circuits were originally carried using a line code called Alternate Mark Inversion (AMI). Later the line code used was B8ZS. AMI did not have sufficient range, and required the application of repeaters over long circuits but also were subject to lightning and cable trouble such as inferior splices and backhoe fade. In troubleshooting these type of services, the *felt* frequency on each conductor is 772 Hz. and the repeaters are usually spaced every mile to 1.2 miles depending on cable size and the whim of the engineers. There is a positive and negative polarity to the side of the repeater. This is also true in HDSL carrier. in splicing this type of service the telcos placed the low voltage side of the repeater cable together and then the High voltage side together in the splice.. The telcos have a powering end to the circuit path and this gives the polarity and the repeaters are typically powered up to 130 volts dc. Usually if you see 130 volts there is trouble because the repeaters are running FULL power to try to compensate for the trouble. They require 60 milliamps and if they cannot get it they try to achieve it by raising the power.
The first attempts to use DSL technology to solve the problem were done in the USA, using the line code 2B1Q. This modulation allowed for a 784 kbit/s data rate over a single twisted pair cable. With two twisted pair cables, the full 1.544 Mbit/s was achieved. The new technology attracted the attention of the industry, but could not be directly used worldwide, due to the differences between the T1 and E1 standards. A new standard was then developed by the ITU for HDSL, using the CAP (Carrierless Amplitude Phase Modulation) line code, that reached the maximum bandwidth of 2.0 Mbit/s using two pairs of copper.
HDSL gave the telcos a greater distance reach when delivering a T-1 circuit. It was marketed originally as a Non Repeated T-1, with a distance of 12k feet over 24 gauge cable. The cable gauge affects the distance. To allow for longer distances, a repeater can be used. The repeater actually terminates the circuit and regenerates the signal. Up to four repeaters can be used for a reach of 60k feet (about 20 km). This reduced the cost of maintenance when compared with AMI-based repeaters that had to be used at every 35 db of attenuation (about 1 mile).
HDSL can be used either at the T1 rate (1.544 Mbit/s) or the E1 rate (2 Mbit/s). Slower speeds are obtained by using multiples of 64 kbit/s channels, inside the T1/E1 frame. This is usually known as channelized T1/E1, and it's used to provide slow-speed data links to customers. In this case, the line rate is still the full T1/E1 rate, but the customer only gets the limited (64 multiple) data rate over the local serial interface.
HDSL gave way to two new technologies, called HDSL2 and SDSL. HDSL2 offers the same data rate over a single pair of copper; it also offers longer reach, and can work over copper of lower gauge or quality. SDSL is a multi-rate technology, offering speeds ranging from 192 kbit/s to 2.3 Mbit/s, using a single pair of copper. SDSL is used as a replacement (and in some cases, as a generic designation) for the entire HDSL family of protocols.

What is E1 ?

What is E1 ?

2007-08-26T21:57:00.001-07:00

E1 (FIRST ORDER EUROPE TRANSMISSION STANDARD)
An E1 link operates over two separate sets of wires, usually coaxial cable. A nominal 2.4 Volt signal is encoded with pulses using a method that avoids long periods without polarity changes. The line data rate is 2.048 Mbit/s (full duplex, i.e. 2.048 Mbit/s downstream and 2.048 Mbit/s upstream) which is split into 32 time slots, each being allocated 8 bits in turn. Thus each time slot sends and receives an 8-bit sample 8000 times per second (8 x 8000 x 32 = 2,048,000). This is ideal for voice telephone calls where the voice is sampled into an 8 bit number at that data rate and reconstructed at the other end.
One timeslot (TS0) is reserved for framing purposes, and alternately transmits a fixed pattern. This allows the receiver to lock onto the start of each frame and match up each channel in turn. The standards allow for a full Cyclic Redundancy Check to be performed across all bits transmitted in each frame, to detect if the circuit is losing bits (information), but this is not always used.

One timeslot (TS16) is often reserved for signaling purposes, to control call setup and teardown according to one of several standard telecommunications protocols. This includes Channel Associated Signaling (CAS) where a set of bits is used to replicate opening and closing the circuit (as if picking up the telephone receiver and pulsing digits on a rotary phone), or using tone signaling which is passed through on the voice circuits themselves. More recent systems used Common Channel Signaling (CCS) such as ISDN or Signalling System 7 (SS7) which send short encoded messages with more information about the call including caller ID, type of transmission required etc. ISDN is often used between the local telephone exchange and business premises, whilst SS7 is almost exclusively used between exchanges and operators. SS7 can handle up to 4096 circuits per signalling channel[citation needed], thus allowing slightly more efficient use of the overall transmission bandwidth.

Unlike the earlier T-carrier systems developed in North America, all 8 bits of each sample are available for each call. This allows the E1 systems to be used equally well for circuit switch data calls, without risking the loss of any information.
While the original CEPT standard G.703 specifies several options for the physical transmission, almost exclusively HDB3 format is used.

HDSL
SS7