3 Technology

Several technologies are available for public safety and security (PSS) networks : TETRA and Tetrapol have been developed for advanced mobile radio requirements whereas GSM and UMTS have been developed for end consumers. These consumer care less about security and quality of service. The operators try to minimize the costs GSM networks cause and try to maximize the services and prices for the end users, for instance with dial tones for € 1.99.

3.1 TETRA

TETRA is an open trunked radio standard that was started in 1988 by the European Commission and the ETSI for the special needs of professional mobile radio needs including not only speech but later also data. In 1990 proposals for the standard were investigated and around 1995 one of the proposals, TETRA-25, was chosen by the ETSI. Nowadays it is simply known as TETRA. (cf. Bekkers01, p. 373 pp)
TETRA is based on TDMA and uses four timeslots with a bandwidth of 25 kHz per carrier. It uses two frequencies for the up- and downlink and use full duplex (a device can send and receive simultaneously) and half duplex (a device can send and receive only alternatingly) use. In the DMO only one frequency and the simplex mode is used.
All the specifications can be downloaded from the ETSI web-page after registration. There are three important specifications: Voice plus Data (V+D), Packet Data Optimized (PDO) and Direct Mode (DMO). But not all the features that are supported are specified (e.g. ISI or open channel) which makes the combination of devices made by several suppliers difficult. Therefore, the TETRA MoU does special compatibility tests.

Functionality Since TETRA has been developed for the special needs of PSS, it supports individual and group calls and additionally broadcast calls, meaning an unidirectional call to a special group in a particular area. The direct mode (DMO) as well as the emergency call are supported. Using the include call a user can be called and added to an existing group call. The open channel allows each group member to speak at any time.

The data services support status transmission and short data services; this is comparable to SMS in GSM networks. The data rate is from 2.4 kbit/s using one timeslot and an high error protection to 28.8 kbit/s using four timeslots and no error protection. Circuit Switched Data for continuous data and Packet Switched Data for packet bases data as well as TCP/IP access are supported so that all common protocols used in the internet can be used, for example WAP. Speech and data can be sent at the same time.

There are additional services like discreet listening which allows a special user to listen to other users in the radio without being recognized. Ambience listening provides the possibility to call a device without a confirmation of a user so that it can be listened to the environment of the device. This feature can be very useful e.g. when an injured policeman cannot reach the device. The priority call is used by the emergency call and can terminate calls with lower priorities (preemption). If a group call has already started, another user can enter this call using the late entry. (cf. BAKOMTETRA01)
The upcoming TETRA2 standard especially provides higher data rates using standards like GPRS which is already in use in GSM networks.

3.1.1 Current Networks

Public Safety Networks TETRA networks in Europe are presently being build in Belgium, the Netherlands, Great Britain, Iceland, Finland, Austria, (cf. Hausmann04, p. 2) and Sweden (cf. PMEV0405). In Belgium, a separate passive alarming system by the enterprise Tecnomen is used which is integrated into the TETRA network.
This technique is also employed for the Summer Olympic Games 2004 in Greece. It aims to meet the demands of about 22,000 people and costs 20 Million Dollars. Rumors say that TETRA will be also be used for the whole country. (cf. Heise031230)
In Austria the contract for the planned TETRA network was canceled in 2003 due to problems in the test operation and the management. The coverage was not sufficient. The operator consortium Master-Talk headed by Siemens was not up to the schedule and could not provide the terminals. Moreover, the costs per terminal rose to 3,276 Euros whereas the Minister of the Interior estimated the costs at about 1,000 Euros in the beginning. (cf. Heise030627), (cf. Hausmann04)
In Norway the fjords have caused coverage problems. The tender has been restarted and Tetrapol is likely to be awarded the contract since it is more suitable for mountainous surfaces. (cf. Hausmann04)

Pilot Project in Aachen There is a small public safety and security network in Aachen. Only ETSI compatible systems have been used, that is to say TETRA. The advertised bidding has been executed by the North-Rhine-Westphalia Interior Ministry and the operation was executed by the police forces. (cf. Funkschau0017) The pilot project was started in July 2001 and finished in June 2003, but this network remains in use. The users are police forces, fire brigades, custom services, the Federal Border Guard and the Federal Criminal Investigation Department. The number of users was 2,000, the area to be covered were 700 square kilometers and it costed 7.7 Million Euros.
End user devices by several suppliers and especially the interoperability were tested. In single and group as well in telephone calls, that are free of charge to the connected authorities, there occurred no problems. But the dynamic encryption between Nokia and Motorola fit not worked since Nokia did not implement it due the fact that this is not part of the TETRA specifications. DMO also caused several problems in connection with emergency calls.
Mobile base stations have been successfully tested for a temporally increasing capacity. Repeaters that can transmit the incoming and outcoming radio into a house in order to provide coverage do also work. Dual-Watch means that a device that is currently in DMO also listens to possible group calls in the network, but none of the devices supported this feature. Data Transmission worked successfully in WAP applications.
Thus, the devices do not support all the features. Before they are used in real life there needs to be extensive testing. The time has to be considered for this evaluation and consultation with the suppliers that should provide good support including firmware updates.
This project was part of the Three-Country Pilot that has tested the interoperation between other TETRA networks in Belgium and the Netherlands. Only speech transmission was tested successfully. The devices were connected to each network and the existing groups could be transfered.
A connection between TETRA and Tetrapol network could be established including single and group calls and data transmissions. (cf. BMIThreeCountry03), (cf. BMIPGBOS03), (cf. Heise030715)
Summing up these issues, this pilot project has shown that TETRA is suitable for the needs of a PSS in Germany.

Private Mobile Radio There are a lot of small networks that are only used by a limited user groups. Examples are the Berliner Verkehrsbetriebe who use it for the underground (cf. PMEVBerlin) (cf. GerpottWalter04, p. 10), the Lower Saxony Police uses TETRA for communication during nuclear radioactive waste containers transportation (cf. TETRAMouPolice03), Stockholm's local public transportation company uses TETRA for the communication of its approximately 2,000 busses (cf. TETRAMouStockholm03) the and Prison Department personnel at Changi Prison in Singapore use it (cf. TETRAMouAsia03).

3.2 Tetrapol

Tetrapol was one of the proposals that could have been the final ETSI standard. But in 1994 TETRA-12 that should later become Tetrapol was not chosen despite the fact that a lot of ETSI participants preferred TETRA-12 over TETRA-25. (cf. Bekkers01, p. 373 pp)
But several suppliers decided to continue the development of TETRA-12, mainly the French supplier Matra. TETRA-12 was renamed into Tetrapol, a label that concats "TETRA" and "police" since the French Ministry of Home Affairs chose Tetrapol for the police forces network. Later attempts to convert Tetrapol to a real ETSI standard were not successful. However, the specifications have been available since 1996 (cf. Bekkers01, p. 385 pp) as Public Available Specifications. (cf. TetrapolPAS)
Tetrapol is based on FDMA and uses 12.5 kHz per carrier, this being the reason it was named TETRA-12 in the first place.

Functionality Tetrapol has the same features like TETRA and a bigger coverage area in contrast to TETRA (cf. BAKOMTETRA01). The upcoming Tetrapol 2004.IP standard is going to eliminate some inadequacies of Tetrapol (handover, end to end encryption) and add IP based functionality.

3.2.1 Current Networks

Public Safety Networks Networks in France, Switzerland, Czechia, Spain Slovakia, Romania and Mexico are already in use. (cf. Hausmann04, p. 2)There are no references for the upcoming Tetrapol 2004.IP standard.

Private Mobile Radio The Berliner Verkehrsbetriebe not only use TETRA but also Tetrapol for the communication between the busses and headquarters. Other users are the Federal Forces and the airports in Frankfurt and Berlin-Tegel. (cf. GerpottWalter04, p. 10), (cf. EADSNetworks)

3.3 GSM/UMTS

GSM was introduced in 1992 and has become the most popular digital radio standard: Today, more than one Billion people use GSM phones. (cf. Heise040223) But these people are ultimate consumers with limited requirements.
UMTS offers a greater bandwidth up to 2 Mbit/s, especially suitable for multimedia purpose like video conferences within a frequency band around 2,000 MHz. But these data rates can only be provided in so called pico cells that have a small radius but can offer the high data rates. Most coverage will be achieved using bigger micro cells and macro cells that provide data rates of about 384 kbit/s and 144 kbit/s and even the macro cells are very small in contrast to the other digital networks that do not provide such data rates.
But even Oliver Mass, director for products development of Vodafone, says that these data rates are not required by public safety networks. (cf. VodafoneNeuUlm02) The primary requirements of PSS network are a good coverage, quality of service and the special call features, not a higher data rate. Thus, UMTS is not regarded as technology for PSS and is therefore not further evaluated here.

In 2001, the Federal Ministry of Interior said that only TETRA and Tetrapol can fulfil the special requirements of a digital public safety radio. (cf. BMI010726, p. 4). But meanwhile, several extensions to the original GSM standard have been put into practice.
Especially Vodafone tries to establish GSM as a cheap alternative in Germany, stating two strong arguments: the network based on existing and then with updated software GSM base stations can be available faster and will be cheaper. The network was still possibly available for the Soccer World Cup in Germany in 2006 and the cost will be only 2.3 Billion Euro. (cf. Vodafone031216).

Functionality GSM supports several voice services, the individual call and two types of group calls: Firstly, the Voice Group Call Service (VGCS) that allows speech transmissions in half duplex mode; the group call can be limited to a specific geographical area. Secondly, the Voice Broadcast Service (VBS) that supports a single voice transmitted to all available device (e.g. an emergency call). These call transmission can get the Full Rate of 13 kbit/s or the Half Rate of 6.5 kbit/s that doubles the capacity of a cell. Encryption is used to ensure privacy.
The Short Messaging Services (SMS) enable mobile users to send short text message with 160 characters either as Point to Point Messaging (a user sends a message to another user) or as Point to Multipoint Messaging (a user sends a message to several users). Additionally, Cell Broadcasting defines the message sending that is not acknowledged by the mobile device.
Data Services support Circuit Switched Data using HSCSD with a data rate up to 57.6 kbit/s and Packet Switched Data using GPRS that can reach over 100 kbit/s and are suitable for internet access. (cf. Harte99, p. 259)
Additionally, there were specified extensions to GSM in 1997 for railway purposes (GSM-R): There were additional group call functionalities (cf. ETSIGSMGroupCall97) and precedence and preemption (cf. ETSIGSMPre97) that are named ASCI.

3.3.1 Current Networks

Besides the many GSM networks in the world that are shown on GSM Coverage, there are some railway operators that use the GSM-R standard (e.g. the Deutsche Bahn (cf. DB04) or a connection between China and Tibet (cf. Heise040307)) but there is no GSM network used for PSS.

Vodafone's Demonstration In September 2002 in Neu-Ulm and in October 2003 Vodafone showed in Wrzburg the functionality of group calls, handovers of data transmissions and end-to-end encryption in an area of 100 cells. A special Dual Mode device supplied by Sagem and DeTeWe that adds TETRA functionality for the DMO that cannot be implemented with GSM was shown as well. (cf. VodafonePraxisnachweis03) (cf. Funkschau0402)

3.4 Comparison

The colors that are used in the following tables allow to gather the grade of fulfillments of the requirements at a glance: Red color means no fulfillment, orange color means almost fulfilled, green means fulfilled and blue is is even better than the requirement.

3.4.1 Main Requirements

TETRA fulfills most of the requirements. Tetrapol is almost as good as TETRA and the upcoming but yet not tested Tetrapol 2004.IP standard will provide better IP based features.
Vodafone's GSM ASCI solution has a better coverage from the possible start since the base stations are already in use and mainly the software has to updated. But it is worse than TETRA and Tetrapol: Mostly the connection to the headquarters has not been tested, although it is a important requirement (cf. VodafoneRealisierung02, p. 17). A basic question is whether the great number of base stations (49,000 in contrast to 8,400 TETRA and even less Tetrapol base stations) will be sufficiently protected. And, of course, if the network goes down both the PSS and the private users cannot enter the network. A dedicated network can be secured in a better way since the millions of private users with different needs do not have to been considered.

3.4.2 Service Requirements

Group affiliation in the Vodafone network is only possible for 25 cells. Especially in cities with little cells (cell radius up to 500 meters) users can lose their group affiliation.
The call setup time should be very fast (less than 0.5 seconds) within user groups. Both TETRA and Tetrapol support this necessary feature. Vodafone's GSM ASCI solution does support this (also using PTT) only in existing group calls. The group call setup time lasts about 2.5 seconds. (cf. GerpottWalter04, p. 20) A simple test with two common GSM cellphones, that were in the same cell, in a rural area near Hanover has shown a call setup time of about 9 seconds. Passive alarming is not well supported by the three technologies. TETRA has to use an extension that is already in use in Belgium. Tetrapol 2004.IP will support passive alarming but there are no experiences yet. GSM already provides a similar service that has been in use for years: cell broadcasting, mostly for special data about the base station. This GSM service can be appropriate to the needs, taking into consideration that the user group of passive alarming mostly consists of voluntary users who can reuse their private GSM cell phones. This idea has rather been neglected by the most recent study (cf. GerpottWalter04).
The low data rates that TETRA and Tetrapol offer in contrast to GSM are not that important. Presently only textual based information like database queries will be transmitted.

3.4.3 Gateway Requirements

Due the fact that TETRA does not contain a standardization for the ISI, there can be problems with base station made be several suppliers. Tetrapol and Vodafone GSM do not have this problem since each have only one supplier.
The old analogue PSS network will still be in use for several years until the digital network is made available in each part of Germany. If the Federal States pay most of the network, some states will have the digital network earlier than others. Consequently, there must be a connection between these both techniques. Vodafone's offer does not contain a solution for this issue.

3.4.4 Organizational Requirements

Tetra and Tetrapol fulfill the requirements completely. Vodafone's solution is far behind: The GSM network would not be independent. The main controller of the network is a foreign operator. The whole infrastructure of Vodafone must be as secure as a dedicated one, but there are much more base stations. There could be an advantage if costs of this investments were shared by the the private Vodafone operator and the one for the PSS network. However, the other GSM operators in Germany T-Mobile, E-Plus and O2 could institute proceedings against the PSS that is paid by the Federation and the Federal States since Vodafone could have advantages over the others.
The frequencies around 400 MHz are especially freed by the NATO for the PSS use and by Vodafone only used by the extended TETRA DMO. Moreover, the licences of the 900 MHz frequencies expire in 2010.

3.4.5 Other Properties

The image below shows which technique the European countries has chosen: There is no uniform PSS network in Europe, both TETRA and Tetrapol are in use.

3.5 Advertising

All the three possible suppliers of the PSS network try to point out the advantages of their solution. But the methods they have chosen are questionable.

TETRA has several suppliers than support TETRA on their own like on R S Bick. Besides the official website of the consortium, there is a German incorporated society named Professioneller Mobilfunk e.V. (PMeV) that seems to care about all the digital network at first sight ("Im Verband Professioneller Mobilfunk e.V. haben sich alle führenden Anbieter von Geräten, Systemen und Netzen für professionelle Mobilkommunikation zusammengeschlossen." (PMEVAbout)). But in fact the PMeV only supports TETRA. The Chairman of PMeV Heinz Bick is also the founder and managing director of R S Bick. (cf. RSBick04)

Tetrapol The advantages of Tetrapol are strongly exposed by an article in the journal Funkschau. At the beginning of this article the authors are introduced as employes of EADS Telecom. But the fact that EADS Telecom is the mayor Tetrapol supplier is not mentioned. (cf. Funkschau0401)

Vodafone has received a lot of free advertising in several magazines. This was due to the new idea to extend an existing GSM network and try to compete with networks that were especially developed for the required needs. Vodafone also provides an expert report by Bernhard Walke (cf. Walke03) who prefers the Vodafone solution so much that he cannot be considered as objective anymore but rather biased. Walke for example states that Vodafone's network provides coverage in all the tubes ("Die Handfunkgeräte-Versorgung in-house und in Tunneln ist fast überall in Deutschland gegeben" (Walke03, p. 5)). But Vodafone says that tubes are partly covered ("Auch Schienentrassen, Tunnel, U-Bahnen, Parkhäuser, etc. sind teilweise versorgt" (cf. VodafoneRealisierung02, p. 35)). The time span between these statements is some months. So I do not assume that Vodafone has vastly improved its coverage in tubes during this time. Thus, this report should be considered as advertisement.