INSTITUTO MUNICIPAL DE PLANEACIÓN

Capítulo III De las Sanciones

INSTITUTO MUNICIPAL DE PLANEACIÓN

1 Traffic Characteristics 5.1

1.1 High-Level Call Characteristics 5.1 1.2 Detailed Call Characteristics 5.1

1.3 Quality of Service (QoS) 5.3

1.4 QoS – Human Factors 5.5

2 Data Usage 5.7

2.1 UMTS Call Characteristics 5.7

2.2 User Profiles 5.9

2.3 Data Symmetry 5.11

3 Traffic Modelling 5.13

3.1 Traditional Methods 5.13

3.2 Packet Data Modelling 5.15

4 Section 5 Questions 5.19

SECTION CONTENTS

At the end of this section you will be able to:

• relate QoS to UMTS service capabilities

• state the general UMTS service aims in respect of the radio environment • describe traffic types likely to be available in a UMTS system and relate them

to QoS

• discuss possible UMTS user profiles and relate these to demographic distribution

• discuss appropriate traffic modelling for UMTS systems

• describe the impact on capacity and coverage of the operation of contention- based physical channels in the UL direction and shared channels in the DL direction

OBJECTIVES

MB2005/S5/v6.2

5.1 © wray castle limited

1.1 High-Level Call Characteristics

Primarily, UMTS will provide customers with two different types of service: Circuit Switched (CS) and Packet Switched (PS).

1.1.1 Circuit Switched (CS)

A specific data rate is chosen at the start of the call, based upon user requirements and service category. This rate may be renegotiated during the call. The allocated resources are solely for the use of that customer. Charging is generally based on the type of service selected and the duration of use.

CS communications are needed for applications which are sensitive to delay, such as voice and videoconferencing.

1.1.2 Packet Switched (PS)

With PS communications there is no permanently established end-to-end connection. Network resources are allocated to users in bursts to deliver packets as they are generated. The network is a shared resource, so at one instant a user may be using the whole channel capacity and at the next none at all.

Packets may be delivered with a required QoS that may influence delay. Charging is generally based on volume rather than time.

Typical packet-based applications include e-mail, file transfer and WWW page download. These applications are delay tolerant.

1.2 Detailed Call Characteristics

Within the general terms of packet- and circuit-switched traffic, a number of traffic types, each with their own agreed set of characteristics, can be described in terms of:

• data rate

• symmetry (whether more data is transferred in one direction than another) • typical usage (duration in terms of switched call, average data transfer volume

for packet services)

• delay as perceived by the user.

5.2

Resources allocated in bursts

Shared resources

Charge based upon volume Delay-tolerant applications Fixed data rate, set at start of call

Dedicated resource for call duration

Charging is generally based upon:

Delay-sensitive applications High-level call characteristics Detailed call characteristics Sub-category 2 - - - Sub-category n Sub-category 1 Type of service Duration Data rate Symmetry Typical usage Delay

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MB2005/S5/v6.2

1.3 Quality of Service (QoS)

Services are generally defined as being either circuit switched or packet switched. Currently, in terms of QoS, these may be treated differently. For CS systems, QoS is consistent and guaranteed. On packet networks, however, congestion leads to increased delays and therefore reduced (and variable) QoS.

Longer term it may be more appropriate to view all services as being delivered by a packet-based network. In this case it must be assumed that adequate QoS guarantees and resource reservations are built into packet-based transmission protocols. To help identify suitable levels of QoS, three factors must be considered for each service type: data rates, average usage and delay.

1.3.1 Data Rates

For CS data, the data rate offered to a user is fixed unless renegotiated during the call. In the packet data context, a guaranteed data rate will need to be offered; this could be a fixed percentage of the maximum nominal rate of data transfer. In this case, the user would subscribe to a minimum guaranteed QoS that must be maintained during periods of congestion. However, under lighter traffic conditions better performance would be expected.

1.3.2 Average Usage

To determine a circuit or network Grade of Service (GoS), it is necessary to know the average usage for each type of customer/service.

For CS services, average call duration is needed, whereas for the packet-based services the average file size is needed, which must take into account overheads incurred by the radio interface or protocol headers. The distribution of these inputs also needs to be known or assumed, i.e. a standard Poisson distribution.

1.3.3 Delay

It is reasonable to assume that customers will be increasingly sensitive to delay, and that QoS demands will increase. For packet-based services, delay targets should be achieved for a percentage of customers. Delay is not just service-sensitive, but UE- sensitive also. For example, Internet radio stations do not deliver a complete file before audio playback begins; sufficient buffering on the terminal device will enable playback of the file as soon as enough of the file has been received to satisfy these QoS demands.

5.4

Data Rate

In document LEY ORGÁNICA MUNICIPAL DEL ESTADO DE MICHOACÁN DE OCAMPO (página 83-87)