ECE 2526 – MOBILE COMMUNICATION

CONTINUOUS ASSESSMENT TEST I

Wednesday, October 13, 2021

MODEL ANSWERS + EXPLANATION

• In general, HLR contains information about all subscribers within a network, while VLR contains more dynamic information relevant to subscribers roaming within the VLR area.

• HLR acts as a fixed reference point for a particular mobile station (subscriber), while its VLR can vary depending on mobility and network design.

• In general, a mobile can operate with one main MSC with its HLR serving many other MSCs each with a VLR

Circuit-switched

Packet-switched

1

2

3

4

5

In basic GSM the maximum data rate is 9.6 kbps per time slot. In GPRS the data is packetized which gives in principle an even lower data rate of 9.05 kbps of which 8 kbps is available for the user. However, in GPRS there are two technologies introduced to increase this data rate. Firstly, the error correction that is used can be adapted to the quality of the radio channel. Secondly, it is possible to use more than one time slot. Further Reading: GPRS - Telecom ABC

Wireless networks can use Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA) or Code Division Multiple Access (CDMA)

While free-space loss is the main loss factor when using the link budget to get the system operating margin, GSM limits the range further when ensuring that TDM bursts do not overlap.Further reading:GSM-location (gsm-modem.de)

In theory, any shape that form tessellations can be used to model cells in a mobile network. However, hexagons are preferred because it provides a better approximation of isotropic/circular coverage

(b) Sectoring(a) Splitting

Circuit-switched core

Packet-switched

Further reading:Advantages of FHSS | disadvantages of FHSS (rfwireless-world.com)

REASONAdvanced Mobile Phone Service (AMPS) was a first generation (analogue) system. It used used analogue modulation, i.eFrequency Modulation (FM).

d

Velocity v = 120 km/hrHandoff capacity , t = 2/60 = 1/30 hrs

Therefore 𝒅 = 𝒗𝒕 =𝟏𝟐𝟎

𝟑𝟎= 𝟒 𝒌𝒎𝒔

Radius, 𝑹 =𝒅

𝟐=

𝟒

𝟐= 𝟐𝒌𝒎𝒔

Gaussian minimum-shift keying (GMSK) is similar to standard minimum-shift keying (MSK), only that its digital input is passed through a Gaussian filter before being applied to a frequency modulator. Because MSK is a continuous-phase frequency-shift keying (FSK), the phase of the carrier is varied instantaneously by the modulating signal.

Further Reading:Gaussian Minimum Shift Keying (eeweb.com)

The extended GSM band refers to 10 MHz that was added to the uplink and downlink 900 MHz band, i.e 880-890 MHz (uplink) and 925-935 Mhz (downlink).The number of ARFCNs are (890-880)/0.2 = 50

1. Paging is a procedure. the network uses to find out a subscriber's location before actual call establishment.

2. Paging is used to alert the mobile station of an incoming call or sms

(a) Link budget calculation

Reuse distance is the number of distinct cells separating two cells which are transmitting on the same frequency. In IS-95 (CDMA) all base stations transmit on the same frequency. Hence the reuse distance is one.