Section 6 Service Information Octet - Discount Coupons · Service Information Octet ... BHCA x MHT 3600 Where: A is the traffic expressed in Erlang (E) BHCA = Busy Hour Call Attempts

Service Information Octet

• Includes :-

• service indicator (SI- 4-bits)

• sub service indicator or network indicator (NI- 2-bits)

• The SI will determine the “User”, e.g. TUP, SCCP, ISUP and the NI will determine which network is concerned, e.g. international or national.

• Subservice Field Codes (NI)

D C B A Spare

0 0 International network

0 1 Spare (for international use only)

1 0 National network

1 1 Reserved for national use

Section 6 – SS7

Service Indicator Codes

D C B A 0 0 0 0 Signaling network management messages 0 0 0 1 Signaling network testing and maintenance messages 0 0 1 0 Spare 0 0 1 1 SCCP 0 1 0 0 Telephone User Part 0 1 0 1 ISDN User Part 0 1 1 0 Data User Part (call and circuit-related messages) 0 1 1 1 Data User Part(facility registration & cancellation messages) 1 0 0 0 Reserved for MTP Testing User Part 1 0 0 1 Broadband ISDN User Part 1 0 1 0 Satellite ISDN User Part 1 0 1 1 ) to 1 1 1 1 ) Spare

Section 6 – SS7

Routing Label

• 32 bits , consists of : • Origination Point Code - 14 bits

• Destination Point Code - 14 bits

• Signaling link selection - 4 bits

• The NI, together with 14-bit point code, allows for four signaling networks each with up to 16,384 point codes.

SLS Originating Point Code Destination Point Code

Section 6 – SS7

Signaling Message Handling

• Discrimination :

• discrimination function compares the DPC in the routing label with the point code of own SP

• If DPC = own SP ; message meant for this SP

• If DPC <> own SP ; further processing performed by routing function

• Distribution :

• distribution function examines Service Indicator to deliver the message to the desired user part

Section 6 – SS7

• Routing :

• routing function determines the signaling link on which the message is to be sent

• concerned with OG signaling messages

• routing table is examined along with DPC in the message to determine the OG SLS available to route the message.

Section 6 – SS7

Signaling Link Management

• Controls the links connected to the SP to maintain certain minimum capability of carrying signaling traffic under normal operation & in the event of failures

» Link activation

• process of making a signaling link ready to carry signaling traffic

» Link restoration

• procedure to bring a previously failed link back into service

Section 6 – SS7

Flow Control

• CCS 7, in common with other transport mechanisms, needs to limit the input of data when congestion onset is detected. The nature of CCS 7 will lead to SP/STP overload congestion being spread through the signaling network if no action is taken. This will result in impaired signaling performance and message loss. In addition to signaling network congestion within a node, congestion will also require action to prevent signaling performance from deteriorating. There is thus a need for flow control within the signaling system to maintain the required signaling performance.

Section 6 – SS7

Exercise

Q1. Name the two different kind of signaling types and compare the two.

Q2. Name the users of the TCAP.

Q3. How many types of connections occur in SCCP?

Q4. Out of following, which is used for monitoring the status of link MSU, LSSU, FISU

Section 6 – SS7

Q5. How many consecutive 1s are allowed in signaling units and why?

Section 6 – SS7

Dimensioning

Section 7 – Dimensioning

Objective

The Trainee will be able to understand:

• Mapping on the air interface

• Microwave planning concepts

• signaling link dimensioning and load sharing

• Routing strategies

• Erlang B, Erlang C

• Numbering plan used in mobile networks

• GPRS concepts


Introduction

In a traditional telephony - signaling means the passing of information from one point to another for setting up and supervision of telephone calls.

• subscriber – exchange signaling (signaling between subscriber and the local exchange)

• inter-exchange signaling (signaling between exchanges).

With the development of the CCITT Signaling System No. 7 the capabilities have been enhanced to be able to handle non-call related data. End user data can be transferred, as with the Short Message Service.


Abis Mapping

Besides the traffic channels, the Abis interface also carries the required signaling information in 64 Kbit/s channels. One signaling channel is normally provided for each transceiver within a BTS for controlling upto 8 subscribers per carrier frequency.


Sig TRX 2

Sig TRX 1

TS 0

BSC

TRX 1

TRX 2

1 2 3

4 5 6 7

0

1 2 3

4 5 6 7

0


TS Arrangement on PCM Link : 1 Sector occupies 2TS for TCH (64 Kbps) 1TS for signaling Total number of Time slot in one PCM 32 Out of which 1 is used as FAS and other for internal signaling. TS available for carrying the information 30 Therefore total number of TRXs that can be cater on one PCM = 30/3 = 10


Example:

Assuming that network has BTSs of 2 TRX in each sector, then max number of BTSs that can share the 1PCm link is:

1 Sector occupy 5TS

Therefore, one BTS occupy 15TS

Hence, totoal number of BTSs are = 30/15

= 2



TS BTS 1 BTS 2 0 PCM Management Information 1 TRX 1 2 TRX 1 3 TRX1 4 TRX1 5 TRX 2 6 TRX 2 7 TRX 2 8 TRX 2 9 TRX 3

10 TRX 3 11 TRX 3 12 TRX 3 13 TRX 4 14 TRX 4 15 TRX 4 16 TRX 4 17 TRX 5 18 TRX 5 19 TRX 5 20 TRX 5 21 TRX 6 22 TRX 6 23 TRX 6 24 TRX 6 25 Signalling BTS1, Sector1 26 Signalling BTS1, Sector2 27 Signalling BTS1, Sector3 28 Signalling BTS2, Sector1 29 Signalling BTS2, Sector2 30 Signalling BTS2, Sector3 31 Control Ring

Microwave Links

A Telecom Network has two main constituent

1. Access Network and

2. Connectivity which is the backbone connectivity.

Optical fiber is most popular for high–capacity routes in Network however microwave radio used in lower capacity routes, in difficult terrain, in private and military communication where the advantage of flexibility, security and speed of installation offered by radio are particularly valuable.


Cellular Network Application

MSC BSC

BTS

BTS


Microwave Hop: It is a bi-directional transmission system

containing 2 DMR one at each end of connecting elements.

The information could be on 2MB or higher interface. The microwave frequency bands and the radio channel spacing in these bands have been all standardized by CCIR.

Some typical frequency bands are 2, 4, 6,7,8, 11 & 14 GHz. Above 11GHz rain attenuation becomes a greater problem and hence restrict to short haul (shorter hop length). Each band is further divided into several blocks of channels which is a pair of frequencies, f & f’ for transmission and reception.


Propagation

Microwave beam passes through the part of the atmosphere, which is in close proximity of surface of the earth. Radio waves, like light waves are also electromagnetic waves, though of lesser frequency, also have the properties of light waves like attenuation, refraction, diffraction, scattering and polarization. While designing the system and engineering link, the effect of all these are to be taken into consideration.

The loss between the transmitting and receiving antenna with


transmission medium as vacuum is termed as Free Space Loss.

Lfs = 92.4 + 20 log d + 20 log f

d = distance in Kms

f = frequency in Ghz


Refraction K-factor

It is the scaling factor that helps to quantify the curvature of the radio beam

K = effective earth radius / true earth radius

True earth radius = 6370 km

The angle of curvature by refraction is denoted by the k-factor, defined as the ratio of the effective earth radius (radius of earth which allow the beam to draw as a straight line) to the true earth radius.


Path Clearance Process

• Microwave Link is based on LOS

• Microwave Path curvature is based on Refraction (K)

• Microwave Path should also have Fresnel Zone clearance to avoid diffraction

Fresnel Zone: The area around the line of sight path which results into a reflection of 180° (half wave length) at the receiver is termed as First Fresnel Zone. The area which results in 2 and 3 half wave lengths are Second Fresnel Zone.


Fn = 17.3 Sqrt ( nd1d2/f D)

Fn = Radius of Fresnel Zone (center point at path)

d1 = distance from one end of path to reflection point (km)

d2 = distance from other end of path to reflection point (km)

D = d1 + d2

f = frequency (GHz)

n = number of Fresnel Zone


Path Profile

Linear Method

• Microwave beam is drawn as a straight line

• The effective earth curvature height (h) is calculated for a desired k-factor

h= (d1d2) / 12.75 k

• Fresnel Zone clearance is then calculated for the same k value

Earth Bulge = Effective earth curvature height + Fresnel Zone clearance


Countermeasures

Flat Fading: • Link Overbuilding (Antenna gains, improved receiver

performance, power)

• Shorten distance between sites

• Path diversity

Selective Fading:

• Space diversity

• Frequency diversity

Equipment Reliability: Hot- Standby arrangement


Space Diversity


Frequency Diversity

Tx 1

Tx 2

Rx 1

Rx 2


Over Reach Interference

f1

f1’

f2

f2’

f1

f1’


Signaling Planning Objective

The main planning objectives are:

• Reliability - disturbances in the signaling should be avoided.

• Robustness - a fault in one part of the network should not affect other parts.

• Simple Network Architecture - the structure of the network should be easy to understand.

• Short Delay Times - to cater for high quality of service.


Purpose: to dimension the correct amount of hardware to meet the requirements.

• Over dimension > inefficiency

• Under dimension > congestion

• Input data: - subscriber data

- network data

- GoS

- equipment limitations

Signaling Link Dimensioning


Simplicity is achieved by introducing hierarchical levels. Hierarchical

networks are flexible and allow fast expansion of the PLMN. Hierarchical networks are also easy to operate and manage.

Major part of signaling network delay is induced in intermediate nodes and not so much on the links (in a properly dimensioned network). Hierarchical network structures are therefore also to be preferred from his point of view.


Definition of Traffic

A = BHCA x MHT

3600

Where: A is the traffic expressed in Erlang (E)

BHCA = Busy Hour Call Attempts

MHT is the average holding time (s)

3600 is the number of seconds per hour


When designing the network, redundancy is of major importance. There

are cases though when separation of the connections on different routes is not plausible. One should then at least consider hardware redundancy.


Documents

Section 6 Service Information Octet - Discount Coupons · Service Information Octet ... BHCA x MHT 3600 Where: A is the traffic expressed in Erlang (E) BHCA = Busy Hour Call Attempts