Mobile Multimedia Platforms

Transcription

1 Mobile Multimedia Platforms Andrew Stirling, Arthur D. Little Ltd., Berkeley House, Berkeley Square, London W1X 6EY, United Kingdom. Abstract With the explosion in mobile telecommunications and increasing competition, mobile telephone service providers and vehicle makers are looking to develop new types of service for vehicle users. So far the services have included information about traffic conditions and support in case of breakdowns. In future digital broadcast and third generation telecommunication systems will be used to deliver interactive multimedia services into the vehicle. This paper looks at platform requirements for supporting the delivery of the new multimedia services. It considers the role of operating systems and networks in determining the flexibility and costs of the system. I. Introduction Mobile services are projected to enjoy rapid growth over the next decade, particularly as mobile data services develop to challenge the dominance of voice traffic on mobile networks. Mobile Internet access will be a key feature of these services, with increasing media richness as higher bandwidth wireless networks are rolled out. Advances in technology have enabled a rapid integration of mobile services into individual lifestyles. Vehicle users will expect increasing choice and scope for personalisation of entertainment and information/news services from experience with Internet-based services at home or in the office. Additional services can be developed to meet the special needs of travellers and vehicle users in particular. For example, traffic information and route guidance services can ease driver stress, whilst entertainment services can help to make journeys more enjoyable for passengers which in turn could reduce driver distraction. Vehicle users are a captive mobile community in that they have few distractions (other than driving) and are therefore likely to appreciate an expanded choice of entertainment and information. In fact telecommunication services are so compelling that vehicle users are and will continue to use them on the move, via personal mobile phones. This presents an increasing hazard to all road users, raising public concern and compelling vehicle makers and their suppliers to develop safer means for drivers to access mobile services. To enhance appeal to customers and for safety reasons, vehicle makers will need to enable safe and effective access to emerging mobile services. However vehicle makers are uncertain about the best way to make provision for new services and their future evolution. II. Adaptable Services Service providers will soon be able to personalise mobile services according to the user's location, preferences, and habits. Knowledge of the user's location is particularly powerful in tailoring services, and more powerful still when combined with other information about the circumstances of user. For example, when the user is known to be driving and the vehicle fuel supply is low, it may be helpful to offer a list of the nearest refuelling stations with directions for finding them. Location can also be used to adjust billing, such that the user might pay less when phoning from the office or home than elsewhere. Primarily, this enables a wireless operator to match the pricing of fixed operator in locations where the user is likely to have a choice, such as at home or in an office. An 'on-line' restaurant guide could offer a list of local restaurants to the user, ranked by proximity to the user as well as other important characteristics (the quality ratings etc.). Other services could include a dynamic air departure schedule for airport users and integrated transport planners for users of trains, buses etc., with automatic updates taking into account current conditions /00/$ IEEE

2 III. New Business Models Mobile service providers seek to increase the number of subscribers they have and the value of services delivered. Since vehicles users are a 'captive market', appropriate services might be used heavily if a convenient and effective means of access is provided. The receiver must enable access to all the service features and deliver them in an attractive way. Experience from mobile communications and digital television services suggest that subsidising the price of vehicle receiver equipment might accelerate subscription growth significantly. However, service providers will need to be convinced that there will be considerable use of the services and that there is a reasonable chance of retaining subscribers. IV. What are the Platform Requirements? A. Definition of Platform A platform is a means of delivering services in a uniform way, regardless of underlying infrastructure (hardware and software). This paper concentrates on the in-vehicle receiver platform. Applications Application Programming Interfaces (API) Operating System Hardware Adaptation Layer: Drivers Hardware: CPU, Storage, Communications/Network Interfaces Wireless WAN GSM, CDMA etc. Figure 1. Wireless LAN Bluetooth etc. Wired LAN D2B, MOST etc. Receiver Platform Architecture Building a receiver platform on widely adopted standards enables more rapid service deployment, easier content and service development and enables easier extension to support future service features. Standards are particularly relevant in the following aspects of the receiver: External Wireless interface(s) (GSM, CDMA etc.) Source Decoding (e.g. for processing MPEG-encoded AV signals) Middleware and Operating System (referred to as the software platform), providing application programming interfaces (API's) which enable application software designers to access various functions of the platform. Internal Vehicle interfaces, including wired and wireless local area networks B. Source Decoding The range of source decoders in the receiver determines the range of content and media richness of services that can be received. Whilst MPEG standards dominate in broadcast multimedia, a variety of encoding standards are used for downloading and streaming over the Internet, for example: MP3 for audio, and proprietary formats such as Real Networks, Windows Media Player etc. Since these formats are continuously evolving it is important to be able to update the source decoders periodically, for example through downloading new software to the receiver. C. Middleware and Operating Systems Middleware is software which provides deviceindependent support for applications, connecting the application on the receiver with both the remote service and with local functions such as user interfaces, storage etc.. To ensure a wider range of available content, the middleware should support widely adopted standards such as Java, TCP/IP and WAP. The use of common middleware on receiver platforms enables service providers to serve larger unfragmented markets. The operating system need not directly impact on provision of services, but is a critical aspect of the platform design. The operating system manages the resources of the receiver, sharing processor time and memory space between applications; it provides an interface between the middleware and the underlying hardware of the platform. Factors affecting the choice of operating system include: Its use of processor and memory capacity Its ability to handle real-time events Support for required middleware (Java, TCP/IP, WAP etc.) Availability of support for communications interfaces (wireless and fixed network)

3 Drivers for the range of hardware interfaces needed by the platform (e.g. to a speech controller, graphical user interfaces and an external audio amplifier). Platform Software Element Middleware Operating System Examples WAP stack, TCP/IP Stack, Java Virtual Machine EPOC, Linux, PalmOS, psos, QNX, WinCE, Table 1. Platform Software Elements F. Integrated vs. Distributed Platform The receiver platform might take the form of a single integrated device with the appropriate interface(s) to wireless networks such as GSM and may contain the processor running the middleware. Integrated platforms are typically more compact and cost less than a distributed system. In a vehicle however, there are many devices and functions to be integrated so that it might not be feasible or desirable for all functions to be completely integrated into a single device. Such integration might be sensible only for basic functions. Other functions could be distributed between different devices connected in a system, allowing devices to be located according to space or for example to suit antennae connections. D. The Multimedia Home Platform The multimedia home platform (MHP), defined by the Digital Video Broadcasting consortium (DVB), is a software environment for supporting interactive broadcast services, based on the Java programming language. The MHP has been defined to enable the largest possible market for interactive services, including e-commerce via television (known as t-commerce). Requirements for the vehicle platform may eventually converge with those of the MHP, enabling access to a wide range of services. E. Future extension of the platform Future extensions to support new services may require new software and possibly new hardware to be installed in the receiver platform. The use of standard interfaces for software and hardware facilitates the upgrading. Upgrades via software downloading are normally preferred, since performance can be enhanced and access given to new services/features without requiring significant user intervention or additional purchases. In this way the maximum number of users can be reached by the new services and fragmentation of the user community is kept to a minimum. Some new services will require additional hardware (e.g. a W-CDMA communications interface) and eventually the processor and memory will be unable to accommodate new service features. TV Receiver Figure 2. User Interface Telephone Amplifier CD Changer Distributed System Architecture V. Centralised vs. Distributed Control In addition to the distribution of functions among devices in a system, there are two possibilities for the control architecture. A. Centralised Control In the case of centralised control, one device is responsible for operating the functions of the system. This controller device may also provide the user interface to the system and can be programmed for a particular model of vehicle. The controller behaviour is a key part of the vehicle s 'look and feel' to the user. In contrast to the controller, other devices in the system (mobile communications transceivers, broadcast receivers etc.) can be generic and be produced in large quantities for lower costs. Vehicle designers are putting substantial efforts into simplifying the vehicle s user interfaces for the control of complex systems. This can be achieved through unifying

4 the user interface so that for example, the driver only needs to look at one place for status information and can control any of the functions via spoken commands. In the example shown below the user interface device also performs the centralised control. TV Receiver User Interface Telephone advanced mobile telecommunications will be used to deliver interactive multimedia services into the vehicle. A. Connectivity Connectivity is the ability of the platform to access services or resources in adjacent or remote devices. Connectivity embraces the communication protocol stacks and the physical transmission media. It also embraces delivery of content (e.g. download of MP3 files) and synchronisation e.g. of contact databases or personal schedules. DVD Changer AV Server B. Thick versus Thin Client Figure 3. Centralised Control B. Distributed Control In the case of distributed control, the intelligence for controlling the system functions is held in more than one device. Typically the control intelligence resides with the device which is most closely associated with a particular function. For example, a navigation controller would be responsible for vehicle navigation and need have no involvement in controlling the vehicle's entertainment functions. A distributed configuration, such as that illustrated below, poses some challenges for presenting a unified user interface. User Interface 1 On a network, servers are devices which provide resources and services whilst clients are devices which make use of the resources and services. By shifting the balance of processing power and storage towards the server it is possible to reduce the cost and complexity of the client, making the client 'thinner'. In the limit, the client device becomes merely a browser (e.g. a web browser) and all the content resides on the remote server(s) (e.g. web hosts). Thus a thin client may be thought of as a browser, unable to operate without a link to a server By contrast, a thick client can browse and access remote resources, but can also operate in a stand-alone mode on its own processor and stored data. It is usually important for a vehicle receiver to operate whether connected to a service or not. Since wireless wide area networks (WAN) are subject to intermittent connection, the vehicle receiver should therefore be a thick client. TV Receiver Telephone C. Downloading vs. Streaming Figure 4. DVD Changer User Interface 2 Distributed Control VI. Platform Communications AV Server Current mobile telecommunications provide only low data rates (e.g. 9.6kbits/ second for GSM data) which are capable of supporting text-based services such as information about traffic conditions, route guidance and support in case of vehicle breakdown. However, within the next few years, digital television broadcasting and Some services accessed by the users may involve downloading of content such as MP3 music files, software and electronic books for 'off-line' browsing. Downloading is particularly valuable in connection with wireless networks, which in general have more limited bandwidth than fixed networks and suffer from intermittent connection. When a vehicle comes into range of a broadband 'gateway' e.g. in a refuelling station, it will be possible to use a wireless LAN such as Bluetooth to provide temporary higher bandwidth Internet access for accelerated content download to the vehicle. In contrast to the off-line viewing supported by downloading, streaming involves the direct transmission and viewing of multimedia. Thus streaming is vulnerable to breaks in transmission, which may be more frequent with vehicle motion. Interruptions will also occur when vehicle travels into regions without network coverage.

5 D. Content Storage: Vehicle Multimedia Server On-board storage within vehicles can be used as a cache for downloaded content. The user could indicate preferences to enable the service to download appropriate material. Examples of content include audio (e.g. in the MP3 format), video (e.g. MPEG-2 format) and data (e.g. cached web pages). [The use of vehicle based storage is analogous to the introduction of storage (on hard disc) in domestic set-top boxes for digital TV reception.] The storage could be included in a multimedia server attached to the vehicle's local area network, providing access to multimedia content via small terminals with screens and headphones within the vehicle. Vehicle-based storage would enable optimum use of wide area wireless networks (GSM-GPRS etc.), such that data can be downloaded using spare network capacity, offsetting real-time delivery problems associated with wireless WAN s. E. Synchronisation Synchronisation is the mechanism by which two collections of data are harmonised with each other. One collection could be held by a central server for backup, accessible via the Internet, whilst the other might be held in a vehicle receiver platform. The receiver's data is needed in the event of an interruption to the vehicle s wireless Internet connection with the server. For example, a vehicle receiver might keep a list of personal contacts details (names, telephone numbers etc.), for use with an in-car telephone. This list of contacts may need to be synchronised periodically with another list e.g. held on a web-server. The new SyncML initiative (supported by IBM/Lotus, Nokia, etc.) aims to create an open standard for synchronisation, through which any mobile device can get access to any data, subject to authorisation. This protocol will be an important enabler for mobile e- commerce. VII. Platform Security Security is crucial to the growth of mobile electronic commerce (m-commerce). It underpins the confidence of users, service providers and content providers. Security embraces: Authentication, where the user of the mobile device and the service provider are validated Encryption, where transaction data and content are hidden to prevent eavesdroppers from gaining access to account numbers or having opportunities to pirate valuable content (e.g. the latest music releases). These security functions are provided through the use of digital certificates, unique keys (codes) and encryption algorithms that make use of the keys. Whilst extra security can be provided through tamperproof hardware (such as smart cards or SIM cards), full security depends on careful design of the entire receiver platform architecture. A minimum level of security needs to be demonstrated to reassure service providers and to ensure that content providers will be willing to release the valuable content needed to make the services attractive. VIII. Networks & Communications Protocols A. Common Communication Protocols The Internet Protocol family (referred to as TCP/IP) will be pervasive in mobile telecommunication networks and is the key to accessing Internet-based services. To promote maximum flexibility the receiver platform should support TCP/IP for external interfaces and over internal networks. In this way the receiver could support multiple browser terminals. Wireless Application Protocol (WAP) is an alternative to the upper layers of TCP/IP, WAP is designed for data communication over wide area wireless links with the frequent breaks of connection, low bit-rates and high latencies for connection set-up. B. Local Area Multimedia Networks Multimedia devices in future vehicles will be interconnected via a multimedia network. Networks help to reduce cable weight and bulk by carrying a multiplex of communications between devices. The type of network required for a vehicle system depends on the volume of data traffic to be carried in a system and the time criticality of its delivery. Some data, such as digital audio and video impose critical timing constraints and high data-rates when being streamed 'live' to an output. Failure to meet these requirements is likely to result in disrupted reproduction of the audio and video signals. Recent developments in wireless technology give the possibility of having hybrid fibre/cable and wireless local area networks within the vehicle.

6 C. Wireless Local Area Networks In the local area, it will be important for personal devices such as mobile phones and PDAs to be able to exchange contact details, meeting appointments, digital certificates of identity etc.. In the context of a vehicle, supply of identity might be the basis of a keyless entry and vehicle activation system. A temporary wireless link between the vehicle and a roadside beacon could be used for road tolling and supplying local traffic information. Personal mobile devices will be able to form ad-hoc local area networks (LANs), using wireless technology such as Bluetooth, and will be able to share functions between themselves and the vehicle's systems. For example a vehicle navigation system could access a route plan which has been pre-loaded in the driver's PDA. Local communications need to be secure against unauthorised access to locally held data or functions. This means that any two devices exchanging data must authenticate each other, possibly with reference to a trusted third party. It also means that the transport of data being exchanged must be protected against eavesdropping or piracy. D. Wireless LANs Wireless LANs provide for communication within the vehicle and within close range of the vehicle. The principal standards are Bluetooth and the Infrared Data Association (IRDA), listed in the table below. Applications of wireless LANs include supporting hands-free telephony. The simplicity of a wireless connection contrasts with the variety of wired connections needed for different makes and models of phone. Short Range Wireless Source Data Rate Infrared (IRDA) <=4 MBaud 10 Range (m) Bluetooth 0.72M Baud Table 2. Wireless LANs Bluetooth is a low-cost wireless networking standard which is expected to be widely integrated into mobile phones. This makes it desirable to support Bluetooth within the vehicle's multimedia platform. In addition to replacing cables in point-to-point connections, Bluetooth supports ad-hoc networking, where a group of adjacent devices can form a wireless network. Such a network might include; mobile phone, PDA, an MP3 player, a digital camera and the vehicle's Bluetooth interface. The vehicle's Bluetooth interface might be integrated in a Bluetooth gateway device linked to the vehicle's multimedia and other networks. Some existing mobile phones and PDAs already support communications via an infrared interface. This type of interface is not very reliable for use in a vehicle: particularly due to its directionality and the relatively high power consumption (compared to RF wireless), leading to shorter battery life for hand-held devices. E. Remote Connectivity Links with remote servers, via the Wireless wide area networks (WANs) will enable users to gain access to a range of services. These services could include the supply of information, news and entertainment and navigation, with traffic-dependent routing and services delivering information, to the vehicle. The platform needs to support the appropriate mobile communications standards for the target market(s). The following table shows some packet-switched wireless WAN examples for Europe. Network Max. Data Rate Realistic Data Rate 1 GPRS 120k Baud ~50kB EDGE 384k Baud ~100kB UMTS 2M Baud 100 to 384kB Table 3. Wireless WANs in Europe Enhanced data rates for GSM evolution (EDGE) and Universal Mobile Telecommunications System (UMTS) offer sufficient bandwidth to support some multimedia service delivery to the receiver. F. Digital Broadcasting Digital broadcast services enable cost-effective mass distribution of rich multimedia content, with high quality audio and video compressed using MPEG encoding. 1 For bearers other than GSM, the quoted capacity applies to downstream data transport (to the user), whilst a lower rate is available in the reverse direction

7 However, broadcast services currently offer less scope for interaction with users than with mobile communications services such GSM and UMTS (in the future). Within a few years, both satellite and terrestrial digital TV broadcast platforms will provide a limited bandwidth return channel, subject to frequency planning in different regions. However, it remains to be seen how suitable these 'broadcast' return channels will be for mobile use. Terrestrial Digital audio and video broadcast services within Europe, are based on a robust modulation technology known as Coded Orthogonal Frequency Division Multiplexing (COFDM), which enables high quality reception within moving vehicles. COFDM is also tolerant of multi-path interference, which severely affects mobile reception of analogue FM radio services. Digital Audio Broadcasting (DAB) transmissions take the form of multiplexes, which may include audio (radio), data and even video services. DAB has only a limited capacity to carry video, both still and moving images. Each DAB multiplex has a capacity of around 4 Mbits/sec.. Of this total capacity, up to 1.5 Mbits/sec. could be set aside for 'auxiliary data' to carry services such as traffic information. Digital Video Broadcasting (DVB) is the most widely adopted of the international Digital TV transmission standards. In its terrestrial form (known as DVB-T), Each 8 MHz RF channel provides a data transport capacity of around 24 Megabits/second, which is sufficient for around 6 TV channels or various combinations of audio, video and data streams. G. Interaction for Broadcast Services User interaction with services can be either entirely within the local receiver or may use a bi-directional link, to interact directly with the service provider. Local interaction takes place with software applications executing on the vehicle's receiver platform. This interaction can be fast and is independent of a wireless return path, giving enhanced robustness. Return paths from vehicles are currently based on mobile telecommunications using GSM-SMS, Cellular Data Packet (CDPD) etc. In the future, it will be possible to support a limited bandwidth terrestrial (or satellite) return path. IX. Platform Applications A. Browsers The receiver platform in the vehicle may support multiple browsers to allow individual vehicle users to access remote services. A browser for the vehicle drivers will need to support both voice input and output for safe and convenient access. The voice-based browser will read out the items on a web-page (e.g. refuelling stations, pizza parlours and hotels) and the driver will verbally select the preferred item (e.g. a particular refuelling station). B. Telematic Applications Telematics applies a combination of wireless communications and information technology to assist people who are travelling. For example, it includes provision for access to traffic data to enable a journey to be time-optimised. The range of data rates for Telematics is limited by the capacity of mobile telecommunication links: typically tens of kilobits/second to hundreds of kilobits/second. C. Multimedia applications Multimedia applications require much higher communication bandwidths than those needed by the telematic applications described above. For example each CD-quality stereo digital audio link will normally require a capacity of around 1.4 Megabits per second. Distribution of a single TV channel within the vehicle might require from 3 to 5 Megabits/second, whilst distribution of a whole multiplex would require around 24 Megabits per second. If multimedia network bandwidth is available then several multiplexes, could be distributed to allow separate selection from a large range of channels at each passenger terminal. D. European Traffic Information Services In Europe, traffic information has been broadcast via the so-called Radio data service/traffic Message Channel (RDS/TMC) on certain FM radio stations. This service provides up to a few hundred bits/second for transmission of data to be filtered by the receiver for relevant information to be announced to the driver. More recently a group known as the Transport Protocols Expert Group (TPEG), including broadcasters and automotive suppliers, has defined an open standard for distribution of traffic information over diverse

8 channels. The traffic information could be disseminated as individualised streams over wireless networks (e.g. via GSM/GPRS) or broadcast (e.g. via satellite services such as DAB) for individual receivers to filter according to current location and planned route to the destination. X. Further Reading [1] Mobile Platforms: a) EPOC: b) WindowsCE/Pocket PC apc/features.asp c) PalmOS: [2] CDMA-based Mobile Telecommunications: a) b) ml c) GSM and extensions: GPRS, SMS and other mobile network bearers : [3] DVB Multimedia Home Platform: [4] SyncML forum: [5] Digital Video Broadcasting (DVB): [6] Digital Audio Broadcasting (DAB) [7] Traffic Protocols Expert Group (TPEG): [8] W-CDMA: [9] Mobile Internet Protocol a) tml d)