Communication Systems involved in planning activities

The EML2 Group focuses its planning activities on many different wireless systems because many heterogeneous communication systems are widely spread and used in everyday life. Therefore there is the need to accurately plan each of them referring to different standards and protocols.

Coverage planning, optimum position planning, electrical configuration planning, optimum antenna orientation planning and offered Quality of Service (QoS) planning represent some of our main activities.

In order to clarify the scientific area of interest, we propose here a brief review of different wireless systems. The picture reported below illustrates the wireless technology evolution time-line.



2G Wireless Systems

 Second Generation (2G) cellular networks use digital modulation format and TDMA-CDMA/FDD multiple access techniques. Among these kind of systems, there are three TDMA standards and one CDMA standard:

1.   GSM (Global System Mobile) which supports eight time-slotted users for each 200kHz radio channel and has been deployed widely in the cellular and PCS bands by service providers throughout the world.

2.    IS-136 (Interim Standard 136) also known as D-AMPS or NADS (North American Digital Cellular Standard) because of its usage in United States only.

3.    PDC (Pacific Digital Cellular), a Japanese TDMA standard similar to IS-136.

4.    IS-95 (Interim Standard 95) that is the popular 2G CDMA standard, also known as CDMA-One, which supports up to 64 users that are orthogonally coded and simultaneously transmitted on each 1.25MHz channel.

These systems rely on digital modulation and sophisticated digital signal processing (if compared to First Generation cellular systems) both in the mobile receiver (MS) and the base station (BS). Usually, 2G wireless networks are designed and consequently deployed for conventional mobile telephone services. All of these networks require a specific wireless planning in terms of signal coverage for the area that has to be served.

 2.5G Wireless Systems

2G systems show a set of limitations: data transmissions are generally limited to the data throughput rate of an individual user (because 2G technologies use circuit-switched data modems that limit data users to a single circuit-switched voice channel) and the only supported user data rates reach 10kbps (too slow for rapid e-mailing and Internet browsing applications). As a consequence of that, new data-centric standards (namely 2.5G) have been developed, in order to support modern Internet applications and higher data rate transmissions in general. Web Browsing (and a new web browsing format language named Wireless Applications Protocol, WAP), e-mail traffic, mobile commerce, location-based mobile services are the most common available applications. Three different “upgrade paths” have been developed for 2G systems:

1)    HSCSD (High Speed Circuit Switched Data) for 2.5 GSM that is a circuit switch technique that permits to a single mobile subscriber to use consecutive user time slots in the GSM standard.

2)    GPRS (General Packet Radio Service) for 2.5 GSM and IS-136 that is a packet-based data network, well suited for non-real time Internet usage (e-mail retrieval, faxes, asymmetric web browsing with predominant download activities).

3)    EDGE (Enhanced Data rates for GSM Evolution) for 2.5 GSM and IS-136 (usually seen as a 3G wireless network), that is a more advanced upgrade to the GSM standard, requires the addition of new hardware and software at existing BS and has been developed to have a common technology path for eventual 3G high speed data access.

 3G Wireless Systems

 3G systems offer new kind of wireless access: multi-megabit Internet access, VoIP communications, increased network capacity, voice-activated calls and so on. Among the others, we cite the so-called 3G W-CDMA Universal Mobile Telecommunication System (UMTS) that is an air interface standard that assures backward compatibility with 2G and 2.5G technologies. It has been designed for “always-on” packet-based wireless service, so that heterogeneous hardware devices (computers, telephones, mobile phones) may all share the same network. Other 3G wireless systems havebeen developed but in this context we prefer to examine more in detail the network planning aspect: in addition to coverage planning considerations (that are typical planning aspects for 2G systems), there are new, more complex issues to be considered: Quality of Service (QoS) in a given area (due to high data rate services requested by the users); advanced handover (or handoff) procedures that transfer an ongoing call or data session from one channel connected to the network to another one; different network behaviour in downlink and uplink sessions (common users download traffic is greater than the upload one). Those aspects need to be considered carefully in planning problems and require new analytical formulations.

 Broadband Wireless Access Systems

 The need for cheap, reliable, rapidly and easily deployable broadband connectivity in emerging countries (usually affected by a wireless communication gap) or the need for broadband connectivity in specific geographical areas where traditional broadband cable services cannot be deployed led to the development of Broadband Wireless Access (BWA) systems.

These kind of systems – also known as Fixed (Broadband) Wireless Access (FWA) or Mobile (Broadband) Wireless Access (MWA) that add specific mobile features (mobility, nomadicity…) – are well suited for rapidly deploying a broadband connection in many instances and this approach is becoming more and more used in “last mile” connectivity scenarios for broadband local loop access. The main advantage in fixed wireless communication systems (if compared to traditional mobile cellular telephone ones) is represented by the well-defined, time-invariant nature of the propagation channel between the fixed transmitter and fixed receivers.

This is the case of the IEEE 802.16 standard, also known as WiMAX, that is a long range fixed and mobile broadband wireless system that covers relatively large areas using both licensed or unlicensed spectrum to deliver connection to a network with high data rates allowing multimedia connectivity (real-time audio and video streaming, high-data rate web surfing and so on…). Usually, WiMAX networks provide mobile or at-home wireless broadband connectivity and are complementary to Wi-Fi (in the sense that WiMAX Subscriber Units, SS, enable connectivity to a set of inner Wi-Fi devices).

WiMAX networks require a detailed coverage planning too.

 Other Wireless Systems

 The planning activity of the EML2 group is also focused on other wireless communications systems and standards, such as the IEEE 802.11 Wi-Fi standard and the RFId systems.