Multimedia distribution system for rural communities

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Multimedia distribution system for rural communities

Tiziano Inzerilli, Roberto Cusani, Riccardo Salvatori University of Rome Sapienza

INFOCOM Dept.

Via Eudossiana 18, 00184 Rome, Italy

Abstract - Wireless technologies has become convenient solutions to easily establish communication infrastructure in remote areas or rural sites where deployment of terrestrial infrastructure is not economically justifiable. For instance, a small village of few hundreds of citizens can be covered by a few interconnected Wi-Fi hot-spots or a WiMAX network can easily interconnect isolated centers over a wide area. In the wireless infrastructure, a middleware layer is in general needed to provide discovery, access and control of services and network resources. In this work1 we are proposing a simple UPnP-based middleware solution for sharing multimedia contents in a wireless infrastructure for a rural environment. The architecture is light-weight and user-friendly, with three main services, a rendering capability selection, a resource location and a content adaptation service.

I. INTRODUCTION

WLAN and WMAN infrastructures are suitable solutions for provision of ICT services within rural communities in remote sites, which can be hardly reached by wireline networks. If a WLAN can easily serve a village of few inhabitants that are concentrated in a small area, WMAN can be used to reach isolated communities over a wide area within a few kilometres. In addition, WiMAX can be adopted to provide access to the Internet, as an alternative to satellite broadband technologies.

Once network connectivity is established access to multimedia contents can be realized by means of a middleware layer assuring discovery, access and control of services [2]. A middleware technology, which is largely adopted by vendors of electronic equipment, is UPnP [3]. Within the DLNA (Digital Living Network Alliance) group [4], UPnP is currently proposed as a viable technological solutions allowing convergence between the Internet, mobile communications and the consumer electronics world.

As far as management of multimedia, within UPnP a special regard has been given to the definition of a minimal standard architecture to use as a basis for sharing of multimedia contents, i.e. the UPnP AV (Audio Video) Architecture [5]. This includes two standard devices, i.e. the AV Media Server and AV Media Renderer for storing and rendering media contents respectively within a UPnP network. A user provided with a UPnP portable device can access a network automatically, discover available AV Media Servers and AV Media Renderers and control rendering of contents.

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This work is partially supported by the Italian National project Wireless 8O2.16 Multi-antenna mEsh Networks (WOMEN) [1] under grant number 2005093248.

In this work are proposing an enhanced UPnP AV architecture in which the user is able to select the most suitable rendering devices for accessing multimedia contents on the basis of its capabilities and physical location. In addition, automatic content adaptation is provided in the AV Media Servers in case the available AV Media Renderers lack support for some specific codecs of stored media. The introduction of these services makes it possible a more natural and effective interaction of the user with the surrounding multimedia service network. Namely, selection of rendering devices based on their actual capabilities and location makes it possible to easily limit the search scope of useful renderers. In addition, content adaptation embedded in the media server brings about an overall robustness to the architecture, which is able to compensate for short and long term lack of codecs support. Other features of this architecture are the modular and re-usable structure, which is compliant with the UPnP Forum design guidelines.

This paper is organized into three main sections. In section II the reference network scenarios and the studied use cases are introduced and discussed. Section III provides the description of the designed architecture and highlights the enhancements with respect to the standard UPnP AV Architecture [5]. Finally, in section III we are describing a prototype architecture developed using the free framework Intel Authoring and Development Tools for UPnP technology and validating the considered use cases.

II. SERVICE SCENARIOS

A. Network scenarios

The service network for the rural community we are considering is based on the UPnP architecture, which provides convenient mechanisms for discovery, access and control of multimedia services. In order to support UPnP service discovery the network infrastructure needs to fully support broadcast to convey service discovery signalling. In the context of a small village or rural area we are then assuming two possible network infrastructures consisting of a set of WiFi hot-spots (HSs) with broadcast support, i.e. for a WLAN and WMAN network configuration respectively.

In the WLAN configuration, a network infrastructure is obtained by interconnecting a number of WiFi hot-spots using an Ethernet-based distribution system. The LAN fully supports broadcast as it is established using the Access Points (APs), heading each WiFi hot-spots, acting as Ethernet-WiFi bridges. We assume IEEE802.11g [6] (maximum range outdoor 100 meters, data rate 54 Mbps, throughput 23 Mbps)

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W iM A X W D S IE E E 8 0 2 .1 1 a H o t-s p o ts V P N O v e rl a y N e tw o rk E x te n d e d V ir tu a l L A N

links in the hot-spots and a Gigabit Ethernet 1000baseT over copper (maximum extension 100 meters) [7]. With 3 hot-spots (figure 1) an area corresponding to a triangle with roughly 85-meter edges can provide an overall throughput of 70Mpbs, which can be exploited for a small village.

Fig. 1. WLAN network scenario

Fig. 2. WMAN network scenario

Conversely, in the WMAN configuration (figure 2), a network infrastructure is obtained interconnecting a number of WiFi hot-spots using a distribution system based on WiMAX [8]. Unlike the previous network, the WMAN infrastructure does not possess native support for broadcast. We assume then that an overlay network using is established onto the WiMAX/IEEE802.11 infrastructure to form a virtual LAN network and assure broadcast support. Such virtual LAN can be built using a layer 2 VPN [9, 10, 11]. Just using a single WiMAX cell as distribution system the network can extend from few kilometres up to 10 Kms and provide broadband access to the distribution system (10 Mbps at 10 Kms).

In both configurations, each WiFi AP provides a DHCP service for mobile nodes in each HS, while a centralized DNS is provided in the distribution system. DHCP and DNS are used by UPnP devices when they enter a new cell and need to acquire IP connectivity.

We then suppose that a user with a UPnP-enabled PDA is roaming in the rural environment and is moving from one

hot-spot to another. The user will be able to discover and use the same set of devices and services in all hot-spots of the rural network.

Fig. 3. Rural community Wi-Fi hot-spot.

B. Example use cases: access to multimedia content

The service scenario we are addressing is focused on multimedia services that can be offered within a rural community and accessed through UPnP in the network scenarios described in the previous subsection.

UPnP allows discovery, access and control of services and satisfies the following requisites:

Simplicity: UPnP devices can be used by a vast public and

has not to be handled by particularly skilled or professional user.

Self-configuration: a UPnP device enters a new network

and access available services and resources without requiring installation of software, such as printer drivers.

Low cost: UPnP is a widely spread solution which allows

limitation of device costs as well as network maintenance. In the following we are examining three possible use cases which can be realized enhancing the standard UPnP architecture for multimedia management [5]. Figure 3 shows the environment in which the user can move and includes various media renderers and a media server.

Use case a): Rendering device capability selection - Let us consider a user who is looking for multimedia contents to play, such as photo, video, music, etc. The user will be provided with a list of contents available in the AV (Audio Video) Media Server and will select one content. In order to access it, the user needs to use an AV Media Renderer capable of rendering the selected content (in some cases a suitable AV Media Renderer might be present inside the user terminal). The quality of the AV rendering strongly depends on the codec adopted for the multimedia content and the capabilities of the rendering devices includes the supported codecs as well as the possible other features such as the screen size.

Afterwards, the user finds out some multimedia renderers which support the codec and are then able to render the multimedia content. She or he will then select an AV

HS 1 HS 2

HS 3

50 m 50 m

Ethernet 1000baseT

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rendering device and finally request the AV Media Sever to deliver the content to the selected AV Media Renderer to play it in streaming mode.

Use case b): Rendering device location selection. The user is notified of some latest news regarding recent events of interest for the citizens of the community. They are presented as headlines in a screen shot on his terminal. Each headline corresponds to a video clip which can be selected. The user wishes to render such contents on a more powerful device (e.g. a TV monitor) with greater AV capabilities than those of the devices that is using and searches it in the list of AV Media Renderers provided through UPnP and selects a high resolution TV screen. In order to guide the user toward the AV renderer the user needs to be provided with his location. The user asks the location of the selected AV Media Renderer and obtains it (an answer can be a map showing its location or a simple message like this: “The available TV monitor is located inside building A”). The user will then reach building A.

Use case c): Content adaptation request – Finally, the user selects a content which no AV Media Renderer can play for lack of codec. The user then requests the AV Media Server to perform a codec conversion and send the content in streaming mode to the TV monitor.

It is worth highlighting that in order to support use cases a)-c), rendering devices should be able to inform the user of their capabilities and location and the Media Server should perform content adaptation. In turn, the client should be able to perform a selection of the rendering device on the basis of capability and location information as well as requesting the media server to perform content adaptation when necessary. This feature has not been standardized in the UPnP Forum. We propose a possible enhancement of the UPnP architecture including the in the next section.

III. PROPOSED ARCHITECTURE

This section describes an overall UPnP Architecture for network scenarios and the use cases presented in section II. The architecture we are proposing, in addition to the services already standardized by UPnP Forum, include three additional services:

• Rendering Capability Selection • Resource Location

• Content Adaptation

Figure 4 shows the overall UPnP AV Architecture. The standard UPnP architecture includes three reference devices [5] for multimedia management, PoCs (Point of Controls), AV Media Servers and AV Media Renderers.

The PoC coordinates the operation of AV Media Servers and AV Media Renderers. The AV Media Server is a device storing multimedia content for selection by users of the network. Its primary purpose is to allow PoCs to browse or search for content items that are available for the user. The AV Media Renderer renders (e.g. display images and/or play sounds) the content obtained from a media server. This

includes a wide variety of devices including TVs, stereos, speakers, hand-held audio players, etc. PoCs can control content rendering as well as the flow of the content by stopping, pausing and seeking for content.

Fig. 4. Overall UPnP AV Architecture.

In a real deployed architecture these devices does not necessarily map onto distinct network nodes. For example a client node might include both the PoC and an AV Media Renderer, i.e. is able to play content without the use of an external device. However, in case the player available in the client does not support the codec of a certain content, the UPnP architecture is flexible enough to allow search and access to more powerful external players.

In Figure 4, services available in each device are depicted with distinct boxes. Grey boxes are the three additional services we have designed for the rural network infrastructure to enhance the standard UPnP architecture.

The AV Media Server contains standard services, i.e. a ContentDirectory Service, a ConnectionManager Service and an AVTransport Service, in addition to the Content Adaptation service enhancing AV Media Server capabilities. Also, the AV Media Renderer contains standard services, i.e. a Rendering Control Service, a ConnectionManager Service and AVTransport Service, along with the Resource Location Service and Rendering Capability Service introduced in our proposed architecture.

As far as the standard UPnP services are concerned, the ContentDirectory Service provides a lookup/storage service that allows clients (e.g. UI devices) to locate (and possibly store) individual objects (e.g. songs, movies, pictures, etc) that the (server) device is capable of providing. The ConnectionManager Service supports description of streaming capabilities of A/V devices, and binding of those capabilities between devices to establish a multimedia session. Each device that is able to send or receive a stream according to the UPnP AV device model will have one instance of the ConnectionManager service. The AVTransport Service enables control over the transport of audio and video streams.

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This service is used to control the “playback” of the content that is associated with the specified AVTransport. This includes the ability to stop, pause and seek contents. Finally, the RenderingControl Service provides a set of actions that allow the PoC to configure the rendering properties. This includes rendering characteristics such as brightness, contrast, volume, mute, etc.

As far as the services we have introduced, the Rendering Capability Service is used by the PoC to find out the supported codecs of the AV Media Renderer. Whereas, the Resource Location Service is used to find out the physical location of the AV Media Renderer inside the rural network. Finally, the Content Adaptation is able to adapt the original codecs of a content stored in the AV Media Server to capabilities of an AV Media Renderer.

A PoC for each discovered rendering device can send a query and get the device location (e.g. a string or a map that represents the location of the AV Media Renderer) and the capabilities through the Resource Location and Rendering Capability services respectively. In case no rendering device is able to play a specific content the PoC can obtain the content’s codec conversion through Content adaptation service.

Figures 5-7 show the message sequence diagram related to the different phases of the signalling for the enhanced AV UPnP architecture. Queries for rendering device’s capability (figure 5) and location (figure 6) are realized with the message exchanges GetCodec ↔ Codec and GetLocation ↔ Location respectively. Requests for content adaptation (figure 7) to the AV Media Server are obtain with the message exchange AdaptCodec ↔ Ack. Following the reception of codec and location information, the PoC selects the rendering device either through direct intervention of the user or automatically on the basis of a suitable embedded algorithm.

IV. IMPLEMENTEDSERVICEPLATFORM

UPnP architecture enables discovery and control between devices in a network, independently of particular the operating systems, programming languages, or physical network connections that are used. In order to validate the architecture presented in section III, we used the Intel tools [12,13] for the development of a testbed.

The Intel software for UPnP helps hardware designers and software developers build easy connectivity into common electronic devices, which can:

• Discover other devices in the network • Remotely control appliances

• Share information among devices and the WWW The tool provides convenient interfaces for:

• Device Discovery • Device Description • Service Presentation • Event Management • Service Control

Figure 8 illustrates the process we followed for developing our architecture with the Intel software, identifies the tools

that have been used and shows where they are used during the development. Search AV contents AV contents GetCodec Codec ack ack

Content transfer (streaming) ack ack AV contents selection AV Media Renderer PoC AV Media

Server AV Media RendererAV Media

RendererAV Media Renderer

AV Media Server AV Media Server AV Media Server AV Media Rend. Select Play Content

Figure 5 – Message Sequence Chart - Rendering capability selection

Search AV contents

AV contents GetLocation

Location

ack ack

Content transfer (streaming) ack ack AV contents selection AV Media Renderer PoC AV Media

Server AV Media RendererAV Media

RendererAV Media Renderer

AV Media Server AV Media Server AV Media Server AV Media Rend. Select Play Content

Figure 6 – Message Sequence Chart – Resource Location selection

Search AV contents

AV contents GetCodec

Codec

ack ack

Content transfer (streaming) ack ack AV contents selection AV Media Renderer PoC AV Media

Server AV Media RendererAV Media

RendererAV Media Renderer

AV Media Server AV Media Server AV Media Rend. Select Play Content Ack AdaptContent AV Media Server

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Service description authoring is the process of creating service descriptions (SCPD, Service Control Protocol Document) by customizing service templates. The Device Builder automatically aggregates well-formed SCPDs and generates embedded code and a sample application. Finally, the Device Validator tool automatically tests devices and verify UPnP and UPnP AV compliance. Also, Intel provides some tools to test UPnP capabilities of designed devices like Intel Device Spy, Intel Device Sniffer, Intel AV Media Controller, and Intel AV Media Renderer.

Figure 9 shows the testbed realized using IEEE802.11g connectivity. It consists of the following devices:

PoC (Point of Control) - Laptop computer with "Intel

Tools for UPnP Technologies". PoC discovers the AV devices and accesses the multimedia services.

Access Point - standard gateway device providing DHCP

and DNS services as well as wireless access to the Internet for the various devices of network.

AV Media Server – It contains some AV contents as video,

photo, music, etc. and includes Content Directory Service, Connection Manager Service, AV Transport Service and Content Adaptation Service.

AV Media Renderers - They are to able to play the

multimedia contents sent by the AV Media Server. They include Connection Manager Service, AV Transport Service, Location Service, Rendering Capability Service and Rendering Control Service.

The testbed in figure 9 was used to demonstrate use cases a)-c). Namely, the operation of the new services, i.e. Rendering Capability Selection, Resource Location and Content Adaptation, was demonstrated. Following the preliminary network connectivity establishment and discovery of the devices in the network, the three services were tested.

The PoC running in the user laptop was used to control all the network resources and services and can be pilot by the user by means of a GUI (Graphical User Interface). Following Rendering capability and Resource Location phases, AV Media Renderer 2 was selected for an MPEG3 streaming session. In order to test content adaptation, the AV Media Server converted a sample media in wave format into MPEG3 and established a streaming session with the selected AV Media Renderer.

CONCLUSION

In this work we have presented a service network infrastructure for sharing multimedia contents within a rural community. The proposed architecture is based on UPnP and can be adopted in both the context of a WLAN or WMAN network environment and support automatic discovery, access and control of multimedia services.

In the architecture we have proposed along with standard services as recommended within UPnP Forum management multimedia contents, we have proposed additional services enhancing the multimedia capabilities for intelligent selection of rendering devices on the basis of their capabilities and

physical location as well as for enabling content adaptation of media.

The architecture presented in this work was validated using the Intel Authoring and Development Tools for UPnP Technology [12, 13] in compliance with the guidelines for development established by the UPnP Forum [3, 5].

Fig. 8. Development Approach.

Fig. 9. Testbed scenario. REFERENCES [1] www.womenproject.altervista.org

[2] Feng Zhu, Mutka and Lionel M. Ni, Classification of Service Discovery in Pervasive Computing Environments, Michigan State University, East Lansing.

[3] http://www.upnp.org/

[4] http://www.dlna.org/en/industry/home/

[5] UPnP AV Architecture: 0.83, © 1999-2000 Contributing Members of the UPnP™ Forum, 2002.

[6] IEEE Std 802.11a-1999 (R2003) (Supplement to IEEE Std 802.11-1999) [Adopted by ISO/IEC and redesignated as ISO/IEC 8802-11:1999/Amd 1:2000(E)] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications High-speed Physical Layer in the 5 GHz Band.

[7] IEEE Std 802.3™-2005/Cor 1-2006 (Corrigendum to IEEE Std 802.3-2005) Carrier Sense Multiple Access With Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications Corrigendum 1.

[8] IEEE Std 802.16™-2004 Air Interface For Fixed Broadband Wireless Access Systems.

[9] http://openvpn.net/ [10] http://www.openssh.com/

[11] Markus Feilner, OpenVPN: Building and Integrating Virtual Private Networks, Packt Publishing Ltd.

[12] Intel Authoring Tool for UPnP Technologies, Intel® Corporation, 2003. [13] Intel Development Tools for Implementing UPnP Devices, Intel®

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