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Air Band Tranceiver
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Vertex Standard VXA-220 Pro VI Air Band Aviation Transceiver List Price: $249.00 Sale Price: $199.00  |
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Vertex Standard's newest addition to the submersible airband portable! The Vertex Standard VXA-220 Pro VI is a compact, stylish, solid and submersible hand-held transceiver providing communication on the International Aircraft Communication Band... |
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Icom IC-A14 VHF Air Band transceiver List Price: $376.00 Sale Price: $198.50 |
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Made with the student pilot in mind The IC-A14 is the ideal flight companion for the student pilot. This radio practically pays for itself by saving pilots both engine hours and fuel during preflight communications with the tower... |
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Vertex Standard VXA-300 Pilot III Air Band Transceiver Nav/Com List Price: $239.00 Sale Price: $245.00 |
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The Vertex Standard VXA-300 is a compact, stylish, solid hand-held transceiver providing communication (transmit and receive) capability on the International Aircraft Communication Band ("COM" band: 118 ~ 136... |
Here are some more information for Air Band Tranceiver:
1. Introduction
GSM stands for the Global System for Mobile Communications. It is a standard initially created to solve the incompatibility of the 1G cellular systems and equipments in Europe. Originally, it operates in the 900 MHz band, but subsequently the 1.8 GHz and 1.9 GHz bands are also supported.
2. GSM System Architecture
There are 6 basic components that formed the system architecture of GSM:
a) Gateway to Wireline System
There are two components within the gateway: the MSC (mobile switching center) and the IWF (internetworking function).
The MSC provides the link between GSM network and the PSTN (public switched telephone network).
The IWF provides the link to internet for IP data traffic.
The MSC and IMF, together with four databases (HLR, VLR, AuC and EIR), formed the NSS (network switching subsystem). The NSS handles the switching of GSM calls between BSCs and MSC to communicate with external networks.
b) Base Station Subsystem (BSS)
The BSS consists of one BSC (Base station controller) and one or more BTS (Base transceiver station). Several BSS connect to one MSC. The BSS provides and manages radio transmission between the MS (mobile station) and the MSC.
The BSC connects and controls a number of BTSs via microwave or wireline. It reserves frequencies, handles mobile handoff between two BTSs within the same BSS, and controls paging.
The BTS consists of all radio equipments such as radio antenna and radio transceivers within one single cell. It performs all signalling related to the radio interface and is the logical location of the antenna.
c) Databases
There are three main databases:
o HLR
HLR stands for Home Location Register. It stores the subscriber information and location information for each user that belongs to the MSC. The HLR also stores the billing information.
o VLR
VLR stands for Visitor Location Register. It stores all roaming subscribers currently within the range of the particular MSC. It contains information of the roaming subscribers such as authentication information, the IMSI (International mobile subscriber identity) and the MSRN (Mobile station roaming number).
o EIR
EIR stands for Equipment Identification Register. It is associated with security issues and shall be discussed in the following section.
d) Security Mechanism
The security mechanism consists of three sub components:
o AuC
AuC stands for Authentication Center. It performs the necessary authentication when a subscriber joins the network and keeps track of the subscribers. It controls access to user data such as the HLR and VLR, by implementing encryption algorithm on all subscribers' request.
o EIR
The EIR is the database for storing the IMSI (International mobile subscriber identity) for each mobile equipment. By matching the IMSI and IMEI (International mobile equipment identity), it can identify any stolen or illegally altered phones and block calls originated from those phones.
o SIM
SIM stands for Subscriber Identity Module. It is a smart card that stores the subscriber's personal data and billing information, and it is inserted into the mobile equipment. SIM is used to authorize the subscriber to access the networks.
e) Air Interface
GSM uses the TDMA (time division multiple access) protocol to control the transmission medium. It utilizes the GMSK (gaussian minimum shift keying) modulation scheme and the bandwidth of the traffic channel is 200 kHz.
f) Mobile Station (MS)
Mobile station (MS) consists of the mobile equipment (ME) and the SIM card. MS communicates with BTS in the same cell where the MS is located via the radio air interface Um.
The ME is basically the cellular phone device excluding the SIM.
3. Conclusion
This article aims to provide an introductory guide to the system architecture of GSM. It attempts to break down the GSM architecture into six logical components, so that readers can have a clear understanding of the system architecture even without technical background.
About the Author:
Dennis Chang is the founder of Lexel Technologies Pte Ltd. He holds a Master of Science (MSc) degree in Communication Software and Networks, and a Honours degree in Electrical & Electronic Engineering from Nanyang Technological University, Singapore.
Prior to founding Lexel Technologies, Dennis had worked as a R&D engineer and senior software engineer in various companies. One of the leading products of Lexel Technologies Pte Ltd is the MoCo SMS Suite series.
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