Chapter 1. Introduction
1.3 Report outline
We have introduced the trend of home networking nowadays and propose new home network system architecture - eHome. In the remaining chapters, we will give more details about home network technologies, eHome system and our implemented eHome prototype.
There are many technologies in the home network area. Generally, we can divide the technologies into two major parts: the home network interface standards and the home network system standards, or called middleware. Besides, they home network interface standards can be further classified into wired and wireless technologies which will be discussed in Chapter 2.
The home network system standard is a system architecture, which may comprise both hardware and software or only software framework, and in which the devices connected by the network can cooperate and discover services among devices.
Some of the home network standards such as HAVi, Jini, OSGi, UPnP, etc. We will introduce in Chapter 3.
Chapter 4, then, will give you an overview of eHome system. We will point out the consideration in designing eHome system and introduce every major component of eHome system. These components are intended to solve some issues of integration of different home networking systems. Besides, in Chapter 5, the implementation of eHome system will be discussed. We will introduce each component of implementation prototype of eHome system and point out our consideration in designing.
Finally, in Chapter 6, we will address some future works and problems which should be improved and modified in our proposed eHome system and implemented prototype.
Chapter 2.
Home Network
Interface Standards
2.1 Overview
Figure 2.1: Network Access Technologies
Figure 2.1 gives us an overview of network access technologies. These technologies can be separated into two major categories: WAN (Wide Access Network) and HAN (Home Network Access). Many standards belong to HAN; for instance, Ethernet [7]
and HomePNA [12], and they can be further categorized according to wired or wireless technologies. We will introduce some important standards and point out their
main features. Besides, we will analyze their disadvantages and advantages.
2.2 Wired Technologies
2.2.1 Ethernet
Ethernet technology is based on IEEE (Institute of Electrical and Electronic Engineers) 802.3 standard [7], which has many revisions because of its interoperability between many manufactures. And the original developer are DEC, Inter and Xerox. The wire structure can be twisted pair, coaxial cable, fiber etc. They are bi-directional, typically are strongly reliable, and thus they are popularly used as the standard choice for PCs and printers. Currently its speed is up to 10 Mbps. The new version called Fast Ethernet support data transfer rates of 100 Mbps. And the next new version, Gigabit Ethernet, will support data transfer rates of 1 Gbps.
Ethernet standard defines two layers of the OSI Reference Model. One is a physical layer, and the other is a link layer. The PHY (Physical layer) is dedicated for how to transmit unstructured raw data over a physical medium, and it also describes the electrical, mechanical, and functional interface to the network. There are many media specifications used for supporting different data rates, media, and topology configurations. Following Table 2.1 will show some common media specifications.
Max. Cable Length Standard IEEE Speed Medium Topology
Half Duplex Full Duplex 10Base5 802.3 10 Mb/s Single 50-ohm RG-58 coaxial
cable (thin Ethernet
Bus 500 M N/A
10Base-T 802.3i 10 Mb/s Two pairs of 100-ohm Category 3 or better UTP cable
Star 100M 100M
10Base-FL 802.3i 10 Mb/s Two Optical Fibers Start 2000M >= 2000M 100Base-TX 802.3u 100 Mb/s Two pairs of 100-ohm
Category 5 UTP cable
Star 100M 100M
1000Base-TX 802.3ab 1Gb/s Four pair of 100-ohm Category 5 or better cable
Star 100M 100M
Table 2.1: Ethernet Physical Layer Media Specifications
The data link layer is focus on how to get data packets in the network. It can be divided to two sub-layers LLC (Logical Link Control) and MAC (Medium Access Control). The LLC is the upper sub-layer in data link layer to support error checking.
And the lower sub-layer MAC is focus on how to get data packet in the network. The
CSMA/CD technique used in Ethernet and Fast Ethernet MAC layer is very important protocol for the later MAC layer development
The CSMA/CD is the abbreviation of Carrier Sense Multiple Access/Collision Detection. There is an interesting metaphor, “The CSMA/CD is a protocol functions like a dinner party in a dark room. Everyone around the table must listen for a period of silence before speaking (Carrier Sense). Once a space occurs everyone has an equal chance to say something (Multiple Access). If two persons start talking at the same instant they detect that fact, and quit speaking (Collision Detection.)”. [9] We map it to Ethernet operation. First when one interface is transmitting data, there will be a signal on the channel called “carrier”. One interface needs to sense signal on the channel before sending the data out. This process is called “Carrier Sense”.
Secondly, the priority of all Ethernet interfaces is the same. And we call it “Multiple Access”. It is possible that two interfaces sense no carrier to send data out simultaneously because every interface has the same priority and the signals take the finite time to travel one end of Ethernet to the other. We call this situation “Collision”.
There is one way to solve this problem. When MAC senses the collision signal, it will stop current transmission and resend after back-off time.
2.2.2 HomePNA
Figure 2.2: HomePNA Networking Topology
2.2.2.1 History
HomePNA (Home Phone-line Networking Alliance) [12], an organization founded in June 1998, is dedicated to the development of standards and specifications for interoperable, home-networked devices that use existing twisted pair phone wire. It was founded in June 1998. The major members of HomePNA currently are .2Wire, 3COM, Agere System, AMD, AT&T Wireless, Broadcom, Compaq, Conexant, CopperGate Communications, HP, Motorola, IBM, Inter etc.
2.2.2.2 Overview
HomePNA standard comprise physical layer and data link layer mapped to OSI reference model. It also defines the MAC (Media Access Control) layer which uses the CSMA/CD as same as the 802.3 Ethernet Standard. And refer to Figure 2.3 the data of upper layer is compatible with frame type in 802.3 Ethernet data frame type.
So the application based on Ethernet can be reused in HomePNA too.
Figure 2.3: HomePNA Data Frame Format [8]
The bandwidth of HomePNA v1.1 is up to 1Mbps in the symmetric mode within distance up to 500ft. HomePNA v2.0 extends the distance to 1000ft. and the speed to 10Mbps. Moreover, the speed is further extended to 100Mbps in HomePNA v3.0 Standard. And HomePNA v3.0 will support the voice-over-HomePNA extend from HomePNA v2.0 by enabling eight simultaneous high-quality voice stream within home. Moreover HomePNA v3.0 can coexist with other services such as ADSL, ISDN and POTS, fully downward compatible with HomePNA v2.0, and support the QoS (Quality of Service) for transmitting data to end-user reliably.
Because HomePNA takes advantages of the existed phone-line used by some technologies such as ADSL, it needs the frequency division multiplex technology to
carry different analog signal on the same phone-line. The analog telephony services use the low part of spectrum: below 35kHZ. ADSL uses spectrum up to 1.1 MHz.
However, HomePNA selected 4 to 10 MHz as its spectrum. HomePNA v1.1 utilizes the PPM and HomePNA v2.0 uses QAM (Quadrature Amplitude Modulation) modulation technologies separately to get more throughputs and to achieve greater robustness. To obtain more details, please refer to [8][10][11][12].
2.2.3 HomePlug
Figure 2.4: HomePlug Networking Topology
2.2.3.1 History
There are many technologies intended to carry the digital data on the existed power line such CEBus, Lonworks, X10 etc. Figure 2.4 is the illustration of power-line network structure of HomePNA. HomePlug [13] Power-line Alliance, established in 2000 is the organization emphasizing on standardization of in-home power-line network. There are 13 founding members include 3COM, AMD, Cisco, Systems, Compaq, Conexant, Enikia, Intel, Intellon, Motorola, Panasonic, Radio, Shack, SONICblue, and Texas Instruments. HomePlug has chosen the Intellon power-line technology as its baseline in the first-generation specification.
2.2.3.2 Overview
HomePlug has defined a robust PHY layer and an efficient MAC layer in order to make a reliable communication on the power-line medium. The PHY is focus on the modulation, coding, and basic packer formats. And the MAC is used to control the sharing of the medium among multiple clients.
The OFDM (Orthogonal Frequency Division Multiplexing) widely used in the DSL and terrestrial wireless distribution of television signals is used as the basic transmission technique in the PHY. HomePlug use ODDM in the robust mode rather than in the continuous mode. HomePlug uses concatenated Viterbi and Reed Solomon forward error correction with interleaving for payload data, and TPC (Turbo Product Coding) for sensitive frame control data fields.
HomPlug also utilizes the variant of well-known CSMA/CD technique protocol as the MAC layer protocol. Several features have been added to support priority classes, provide fairness, and allow the control of latency. The MAC also added the 56-bit DES (Data Encryption Standard) to provide the security of data transmission. It is probably announced by Intellon Corp that the data rate of HomePlug currently is up to 14 Mbps and 100 Mbps in [15]. HomePlug has released HomePlue 1.0 specification in June 2001. And the next generation HomePlug Specification will support distributions of data and multi-stream entertainment including High Definition television (HDTV) and Standard Definition television (SDTV) throughout the home. More details about HomePlug, please see the references [13][14][15][16].
2.2.4 HomeCNA
Figure 2.5: HomeCNA Networking Topology [18]
2.2.4.1 History
HomeCNA (Home Cable Network Alliance) [17] is established in April 2001.
“HomeCNA Vision: Leverage the preponderance of coaxial wire in the home as the networking medium for entertainment, voice and data distribution in the connected home” described in HomeCNA Alliance presentation [18]. Figure 2.5 is the brief of HomeCNA Networking topology.
2.2.4.2 Overview
Figure 2.6: HomeCNA : Five Networks – one cable [18]
HomeCNA is an alliance focus on developing a coaxial coax solution that will distribute entertainment, telephony, voice, data, and controls simultaneously on the coaxial cable. The coaxial is common at home recently. And HomeCNA compatible products will coexist with existing coaxial services. Besides, The interoperability with other organizations that develop the home networking system standards such as OSGi is considered too. Figure 2.6 is the frequency band allocation of HomeCNA. Different network services are allocated into the different frequency bands. So those services can be coexist in the same coaxial cable.
The bandwidth of HomeCNA is up to 100 Mbps and can be extendable up to 400 Mbps. Besides it also support full QoS for video, audio and telephony through IEEE 1394 networking. See [17][18] to get more detail data bout HomeCNA.
2.2.5 IEEE 1394
2.2.5.1 History
The predecessor of IEEE 1394 (1394-1995 IEEE Standard for a High Performance Serial Bus) [19] is the “FireWire” which was conceived in 1986 by Apple Inc. The first version specification of this link was completed in 1987. Then it was adapted as IEEE 1394 standard in 1995 by IEEE (The Institute of Electrical and Electronics Engineers). IEEE 1394a is completed in 1998 and IEEE 1394b is introduced in 1999.
Furthermore, IEEE 1394b is downward compatible with IEEE 1394 and IEEE 1394a.
2.2.5.2 Overview
IEE 1394 is the digital link specification focus on multimedia interface and has many features, for example, the low-cost, high-bandwidth real-time data communication and so on. It is very common standard interface in multimedia device such as DV, Digital Camera, DVD Player, VCRs, PCs, etc. IEEE 1394 support two data transferring mode – Asynchronous and Isochronous. The Asynchronous data transferring mode emphasizes more on guaranteed data delivery but less on guaranteed timing. The Isochronous is opposite, it emphasizes more on guaranteed timing and less on guaranteed data delivery. Therefore the Isochronous is quite suitable for multimedia data. And the Isochronous has the features such as no error correction, no retransmission. It always transfers data by broadcasting in a one-to-one or one-to-many fashion.
The bandwidth of IEEE 1394-1995 is up to 50 Mps within distance up to 4.5 meter. IEEE 1394a supports the speed of 100Mbps, 200Mbps and 400Mbps. IEEE 1394b extends the distance to 100 meter and data rate up to 800 Mbps further. The next version of the standard will support up to 3.2 Gbps data rate. Moreover, IEEE1394 standard also support play and plug so user do not need to reset network when they add or delete IEEE 1394 devices and up to 63 device attached via a single bus connection.
2.2.6 USB
2.2.6.1 History
The first version, USB (Universal Serial Bus) v1.0 specification [20], was introduced in January 1996, and the second version, USB v1.1 [21], in September 1998. In April 2000, the newest version, USB v2.0 specification [22], was introduced. The major members of USB organization are IBM, Intel, Philips, Microsoft, NEC, Northern Telecom and HP etc. Because Microsoft add USB support in their Windows products started since 1998, USB become the most common interface for high-speed data transmission currently in the PCs. Besides, there are more and more peripheral devices use USB as their communication interface to PCs.
2.2.6.2 Overview
Figure 2.7: USB Network Topology
Figure 2.7 is the network topology of USB system that is host controlled. There are up to 127 devices, which can be connected to a single USB bus by using USB host controller, for example, the PC and USB hubs. A root hub (the host controller of Figure 2-7) can directly connect up to 7 USB hubs, and each hub on the root hub can be, in turn, connected to seven hubs, etc. to a maximum of seven tiers and 127 ports.
This kind of network topology is generally called tiered star topology. A “Compound Hub” in USB standard means a USB peripheral device has a USB hub build into it, so it is comprised a function and one or more hubs. Besides, USB supports
plug-and-play and hot plug; therefore, if you plug the device directly, it will be configured automatically. Besides, the maximum length of USB cable is up to 5 meter.
There are two speed modes in USB v1.1 – 1.5Mbps (Asynchronous mode) and 12Mbps (Isochronous mode). USB v2.0 provides higher performance than USB v1.1.
The speed of USB v2.0 is promoted to 480Mbps current, and it is also downward compatible with USB v1.1 speed modes. So when the peripheral device does not support USB v2.0 speed mode, USB v2.0 host will use the lower speed mode of 1.5Mbps or 12Mbps determined by peripheral device to work with it. Besides, USB v2.0 also supports a special transmission mode – OTG (On-The-Go). OTG is a specification allowed USB peripheral device can communicate each other without host. The more detail please refers to On-The-Go v1.0 specification [25]. And some related collections of USB technology is listed in [24].
2.2.7 RS-232
2.2.7.1 History
RS-232 was introduced in 1960, and is currently very common and widely used communication interface especially in PC and Industry field. It is standardized as EIA232 by EIA (Electronic Industries Association) [27]. The third version is RS-232C which is the standard of choice of PC in 1969. The fourth revision called RS-232D adopted in 1987. The newest version is named EIA232E introduced in 1991.
2.2.7.2 Overview
RS-232 is simple and low-cost network interface. It is a single-ended data transmission system. It uses a single wire for data transmission. So it is much useful to support two-way communication using two wires: one is for receiving data, another is for transmitting data. RS-232 utilizes the negative logic to identify the signal status (or logic status). In this case, it uses the negative voltage level (-3V to -12V) to represent ‘1’, positive voltage (+3V to +12V) to represent ‘0’.
Figure 2.8: RS-232 data frame format
Moreover, RS-232 uses the asynchronous mode as its data transmission mode. So it needs a start bit for representing the start of data packet and a stop bit to represent the end of data packet. Besides, the length of data packet of RS-232 can be 5,6,7 or 8 bits.
Furthermore, it also can add a parity bit, which can be odd or even parity bit form for error correction. The speed of RS-232 can be 1200bps, 2400bps, 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, 115200bps or higher. Figure 2.8 depicts the brief waveform of RS-232 signal.
2.3 Wireless Technologies
2.3.1 Wireless LAN - 802.11
2.3.1.1 History
IEEE 802.11[28] is a very popular WLAN (Wireless Local Area Network) standard in the world and the responsibility of IEEE 802.11 Working Group is to develop the international standards for WLAN. And the Wi-Fi Alliance is the wireless standard group formed in 1999 to certify interoperability of WLAN products base on IEEE 802.11 specification. And now, there are many standards developed by IEEE 802.11 Working Group such as 802.11b, 802.11a, 802.11b etc. The 802.11b standard is the first finalized specification in September, 1999 by IEEE 802.11 Task Group b and it is current very popular and already has many compliant products in the world.
2.3.1.2 Overview
IEEE 802.11b chooses DSSS (Direct Sequence Spread Spectrum) as its modulation scheme in the physical layer. Its operation frequency band is 2.4GHz, the unlicensed ISM (Industrial Scientific and Medical) band, and the maximum data rate is up to 11
Mbps.
IEEE 802.11a is another standard version of WLAN. It chooses the OFDM as its modulation scheme and the maximum data rate is promoted to 54 Mbps. But it chooses the 5GHz band to be its operation frequency band. The 5GHz band has less interference than 2.4GHz band but not the unlicensed band in each country. By description above, we can know IEEE 802.11b and 802.11a are incompatible due to they adopt the different modulation scheme and operation band.
IEEE 802.11g is the standard focus on downward compatible with extension to the existing IEEE 802.11b and improves the data rate exceed 20Mbps. Due the MAC (Medium Access Controller) of IEEE 802 share a common LLC (Logic Link Controller), so all the services, such as the file sharing, http, e-mail etc. in the wired Ethernet, are made available to wireless Ethernet too.
IEEE 802.11 adopts the CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) as its MAC protocol. CSMA/CA is similar to CSMA/CD in the wired Ethernet MAC. It like CSMA/CD utilizes a “listen before talk “ mechanism to control access to share the same medium. But there no way to make sure that there is no collision between wanted client/receiver and server/transmitter due to it is possible existed a “hidden” node which wants to transfer data to receiver and is within range of the receiver but out of range of the transmitter. So we cannot monitor the idle or busy state of the medium while transmitting. Therefore IEEE 802.11 adopts the CSMA/CA can solve the above problem efficiently to replace CSMA/CD. The more detail information please refers [28][30][31].
2.3.2 BlueTooth
2.3.2.1 History
BlueTooth SIG (Special Interest Group) [32] was founded by Ericsson, IBM, Nokia, Intel, and Toshiba in February 1998. The mission of BlueTooth SIG is to develop an open standard for short-range wireless technology called BlueTooth. L. M. Ericsson of Sweden invented BlueTooth technology first in 1994. The first version of specification, BlueTooth V1.0b, is released in December 1999 and the second reversion, BlueTooth V1.1, in February 2001. Moreover, the second version is downward compatible to v1.0b.
2.3.2.2 Overview
BlueTooth is an open standard version of WPAN (Wireless Personal Area Network).
Identical to IEEE 802.11b, BlueTooth v1.x adopts 2.4 GHz as its operation frequency band but it utilizes FHSS (Frequency Hopping Spread Spectrum) as its modulation scheme. However, compared with IEEE 802.11, BlueTooth has different market partition The hopping frequency of BlueTooth is 1600 hops per second, the frequency spectrum is normally divided into 79 channels with 1 MHz channel spacing per channel. The maximum of transmitting distance is up to 10 meter at 0 dBm transmitter RF power and up to 100 meters at 20 dBm.
BlueTooth supports two data transfer modes, one is ACL (Asynchronous Connection-Less) for data packet, and the other is SCO (Synchronous Connection-Oriented) for voice packet. The maximum of data rate of ACL is up to 723.2 kb/s asymmetric (and still up to 57.6 kb/s in the return direction) and up to 433.9 kb/s symmetric.
Figure 2.9: BlueTooth Scatter net Network Topology
The network topology of BlueTooth is a master-slave based Ad-Hoc network. It supports up to 7 slaves with a single master in a piconet organized into groups of two
The network topology of BlueTooth is a master-slave based Ad-Hoc network. It supports up to 7 slaves with a single master in a piconet organized into groups of two