VoIP - Power via Ethernet LAN Network using Twisted Pair Premise Cabling Systems

Transcription

1 VoIP - Power via Ethernet LAN Network using Twisted Pair Premise Cabling Systems Technical background information about Power over Ethernet described in standards document IEEE 802.3af and use for Voice over IP applications. May 2005 Author: W.Wahl (Product Manager EMEA) A publication of Tyco Electronics A publication of Tyco Electronics

2 Contents 1. INTRODUCTION 3 2. STANDARD IEEE 802.3AF 3 3. POWER SOURCING EQUIPMENT 4 (PSE) 4. POWERED DEVICES 5 5. POWERED DEVICE CLASSES 6 6. VOIP AND IEEE 802.3AF 6 6. IMPACT TO PREMISE CABLING ADVANTAGES & SAVINGS THE FUTURE AMPCO POWER CONVERTERS FURTHER INFORMATIONS 16 2

3 1. Introduction Since a longer period of time the idea using premise cabling networks defined by TIA 588, EN or for energy transmission on top of information signals has been considered: transmission of phone or data signals and feeding end devices with power at the same time. These end devices could easily work without any external power cord and transformer. This idea is forced by the application Voice over IP (VoIP). Phones on every desk are connected to the Ethernet Network und source their energy out of the same universal infrastructure. There is no more need for a dedicated ISDN or analogue network for phone services which makes the idea very attractive as huge cost savings can be realised. At the beginning the manufactorers' concepts of VoIP devices were very different, after finalisation of the standard for the Power over Ethernet (PoE) application, a change to standardised concept can be expected to guarantee compatibility between devices of various manufactorers. 2. Standard IEEE 802.3af The standard IEEE defines the Ethernet variants 10 Base-T (Ethernet), 100 Base-TX (Fast Ethernet) and 1000 Base-T (Gigabit Ethernet), which can be found in more than 90% of today s networks. Other protocols like ATM and Token Ring have been replaced in many cases by Ethernet during the past years. Part 3 of IEEE 802 describes Carier sense multiple access with collision detection and Physical layer specification". In addition to the specification of Ethernet protocols and their physical layers in the amendment IEEE 802.3af power transmission is defined: Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI)". This section describes an optional power source free of data transmission which can be used with the same physical layer as defined for Ethernet. This unit allows data devices to source energy via the same premise cabling system as data. Energy has to be transmitted together with 10 Base-T, 100 Base-TX or 1000 Base-T using one single interface (RJ- 45) to the user device. With in RJ- 45 connector s four pairs of contacts are defined: Pin 1&2, Pin 3&6, Pin 4&5 and Pin 7&8. Protocols Ethernet and Fast Ethernet use pairs 12 and 36 for their data transmission leading to two different concepts for energy transmission: a) Use of same pairs 12 and 36 (Inline-Power, Phantom-Power) b) Use of non-signalling pairs 45 and 78 (Midspan-Power) For Gigabit Ethernet 1000 Base-T no unused pairs exists that's why method b is not detection (CSMA/CD) access method and physical layer specification". 3

4 3. Power Sourcing Equipment (PSE) Power sourcing devices (Power Sourcing Equipment, PSE) can be found at two locations within a link. Either directly integrated into the switch (Endpoint PSE) or alternatively as midspan injector. Power feeding switches use either Mode A or B (see table1) or both andsupport 10 Base-T, 100 Base-TX and 1000 Base-T. Understandably links must not be fed with power unless the end devices are checked to avoid possible damage or destruction. To secure none of the connected devices gets damaged, feeding power is only allowed if end device has sent a signal to be ready for power. RJ-45 Mode A Mode A Mode B Pin MDI-X MDI alle Table 1: PSE Modes 4

5 4. Powered Devices Power consuming devices (Powered Devices, PD) should be resitant against pole reversal. The powered device (e.g. the VoIP phone) has to at least accept one of the mode A variants and mode B (see Table 2). With other words this means all energy comsuming end devices are standards compliant to IEEE 802.3af, if they support Mode A (Inline-Power, Phantom-Power) and Mode B (Midspan-Power). The end device should be able to select wire pairs where power is received. This guarantees VoIP running as well on older four wire ("Quad") premise cabling or dedicated telephony systems with only two pairs per telecommunications outlet. For the connectors and cables IEEE 802.3af is no challenge as the application has been developed based on the existing premise cabling standards. Category 5E according TIA 568 or Class D according IS or EN with Category 5 components allows IEEE 802.3af to be used with 10 Base-T, 100 Base- TX and 1000 Base-T. RJ-45 Mode A Mode A Mode B Pin MDI-X MDI alle Table 2: PD Modes 5

6 5. Powered Device Classes A powered device should be classified by apower sourcing device via class informations.by doing this, the maximum powercomsumption of the end device when in usewill be defined. Class0 is default setting.to adjust the powermanagement of Power sourcing devices, the powered device can send a code for class 1 to 3. The classification is done based on the power consumption of the device. Maximum input voltage at the device is 57 Volts with maximum 0,4 Ampere. When a PSE is detecting a PD, thepower will be carefully ramped up. If the PSE is not detecting and classifying the PD correctly, power must not be connected to avoid any damage caused to the device. Class Mode Max. Power 0 default Watt 1 optional Watt 2 optional Watt 3 optional Watt 4 not allowed for future use Table 3: PD Classes 6

7 6. VoIP and IEEE 802.3af Voice over IP is the first commercial use of IEEE 802.3af Power over Ethernet standard. Next chapter descibes the historical development with a little more details: Historical Background: The first attempts to use Voice over IP can be found in the beginning of the 90ies. Via sound cards in personal computers voice data was received connecting a microphone and digitalised. Was the computer connected to the Internet these data could be sent to an adequate user. Did both parties sender and receiver use a special software connecting to an IP-server to send the voice data packages, in a poor quality phone calls could me made worldwide at a very low cost. Both users just required a connection to the Internet. One reason of the very slow response times and the resulting poor quality was caused by voice data packages been transmitted the same way as others like s, FTP-downloads, HTTP-applications etc. Telephony is a very time critical application, delays caused by too much data have to - as far as possible - be avoided. In the following years the software for telephone via Internet became more and more comfortable and allowed more than two users same line. Microsoft Netmeeting might be today's most known application for software telephony. One big advantage of data packaged telephony is, more logical connections can be managed same time via one line, which led in the provider business to a significant cost reduction, as only a small percentage of lines need to be installed compared to the old analogue telephone system. In the past one line was necessary per call. Today most phone connections within the telecommunications backbone worldwide are data packaged and the number of physical lines has been reduced a lot with an even higher number of logical lines. VoIP came into the offices First of all there are two things necessary to run VoIP phone in an office a) an Ethernet port with min. 10 Mbit/s b) a power supply for the phone Similar as in the prior descibed software telephony solution VoIP phones digitalise voice and send the data using the Ethernet protocol into the network. The amount of data sent is not really high (some few kbit/s). A RJ-45 Ethernet port is requred at the VoIP phone and a RJ-45 patch cord. For receiving power in pricinciple there are two options: 1) External power source / power adapter 2) Internal power source via network 7

8 The second options is of course the more interesting one as all external power adaptors and power plugs can be removed. This solution is covered by IEEE af. Today most available VoIP phones still work with external power adaptors as many switches do not offer power feeding for end devices yet. Additionally the standard was not finished at the point in time when many phones have been already sold to the market. Next logical step using IEEE 802.3af would be feeding the power from the panel side and get rid of all power supplies in the work area. Picture 2. Cisco Power Patch Panel This means, between switch and patch panel a power patch panel as shown in picture 2 will be installed. The switch is delivering Ethernet data packages on Pins 12 & 36 of the RJ-45. It is connected to the power patch panel (IN) using a RJ-45 patch cord. The power will now be added to the unused pairs 45 & 78 (see Midspan- Power Chapter 3), this means the midspan PSE is working in mode B. The patch cord connected to the power panel (OUT) carries now Ethernet signals on 12 & 36 plus power on 45 & 78. There are a few points of dissadvantage with this solution: 1) An additional element needs to beadded into the rack which can cause severe space problems in highly loaded distributor racks. 2) The ammount of patch cords used in the rack doubles when using power patch panels. 3) Cable and connectors use al 8conductors, 4 wire cabling and sheath sharing is not possible. 4) No support for Gigabit Ethemet applications by the standarts. 8

9 Professional VoIP in the office If you go one final step further with the idea about power patch panels, the powered patch panel will be integrated into the switch. Picture 3 shows a Cisco Catalyst 6000 series with an optional daughter card providing Inline- Power directly from the switch. In this mode Ethernet signals (AC) and power (DC) are transmitted over the same two pairs 12 & 36 (refer Phantom-Power and Inline-Power in Chapter 2). This means the endpoint PSE-switch is working in mode A. This solutions shows some strong advantages to the one described before: 1) Less space consumption in the rack as of no additional equipment 2) No additional patch cords 3) VoIP can run on old four wire systems 4) Support of sheath sharing 5) Support of Gigabit Ethernet Keep in mind that a switch with integrated power has a lower life time and you have to pay for power source again with every switch change which is a negative point. Voice over IP Phones After the evolution of power sourcing devices the following paragraph focusses on different VoIP phone concepts. In general four concepts can befound: 1) Power via external adaptor and RJ-45 Ethernet data port 2) Power via external adaptor and integrated RJ-45 Fast Ethernet switch 3) Power via RJ-45 from the Network and integrated Fast Ethernet switch 4) Power via RJ-45 and integrated Fast Ethernet port First of all the outer shape of VoIP phones and ISDN phones are the same. They are very similar and it is difficult the see which is what. Most VoIP phones today offer much more functionality and comfort than ISDN phones can deliver. Concept 1 is obviousely the most trivial as power is delieverd by an external adaptor and the phone does have a Fast Ethernet port. Voice data is sent and received over Pin 12 & 36 of the RJ-45. 9

10 Only a free network port in the telecommunications outlet is required plus a free power socket. The phone behaves like a standard PC or printer within the network. As an example for such a solution EADS M 780 (see picture 4) is shown. This phone can be upgraded with an optional module from an ISDN to a VoIP phone. Concept 2 shows a VoIP phone with an integrated switch, which means the personal computer will be connected as a slave behind the phone and both devices share the 10/100 Mbit/s connection to the LAN. This solution might be interesting if a not sufficient number of Ethernet ports does exist and adding of an extra link is not possible. A problem is the low data rate with time critical information conflicting the high data rate with low real time requirements of the personal computer. Does the phone additionally offer compliance to IEEE 802.3af to receive power from the LAN, supporting Midspan and Phantom power concept 3 is discussed. This VoIP phone concept works everywhere an Ethernet port for the computer can be found. It can source the power either over IEEE 802.3af from the Network or via an external power adaptor. Today concept 3 is the most known concept at the market place. As an example Cisco 7960G is shown in picture 5. 10

11 Concept 4 is the final step. The power is sourced according IEEE 802.3af via the RJ-45 port and the phone is connected with a dedicated LAN connection to the central switch in the floor distributor. Mini switches inside of the VoIP are not needed any more. The switch in the distributor supports Inline-power and feeds the VoIP phone on pins 12 & 36 of the RJ-45 with data and power. The personal computer is connected separately to a faster network connection. Manufactorer Produc Acc. IEEE af Integr. Switch Ext. Power 3 com NBX 2102 No Yes Yes Alcatel e-reflexes Yes No Optional Cisco 7902G Yes No Optional Cisco 7095G Yes Noi Optional Cisco 7910G Yes Yes Yes Cisco 7912G Yes Yes Optional Cisco 7940G Yes Yes Yes Cisco 7960G Yes Yes Yes DeTeWe OpenPhone 63IP Yes Yes Optional DeTeWe OpenPhone 65IP Yes Yes Optional EADS M780 No No Yes Nortel i2002 No, only mode B Yes Optional Nortel I2004 No, only mode B Yes Optional Siemens OptiPoint 600 Office Yes Yes Optional Siemens OptiPoint 400 Yes Yes Optional Tenovis T3 Yes Yes Yes tiptel innovaphoneip 200 Yes Yes Optional tiptel innovaphoneip 202 Yes Yes Optional tiptel innovaphoneip 10 No No Via USB 11

12 6. Impact to Premise Cabling Planning and implementing a premise cabling system according TIA 568, IS or EN following points should be covered: The links have to fullfill at least Category 5E / Class D requirements. Dedicated separate phone cabling systems are removed. The number of ports planned in the past for ISDN or analogue phones should be added to the LAN infrastructure in the future. VoIP phones require same as personal computers an Ethernet connection with 10 or 100 Mbit/s that at least category 5 components (cable, panels, outlets and cords) are required. Practical experience shows three ports per desk cover most of the demand in various scenarios. The main difference to the past is that instead of planning two Ethernet ports and one ISDN port three Ethernet ports should be installed in the future. AMP Netconnect products fullfill the requirements in regards to voltage proof and can carry the current according IEC (components) and TIA 568, IS and EN (cabling system). The application Voice over IP uses maximum 57 Volts DC at maximum 0,4 Ampére with a maximum end device power consumption of Watts. 12

13 7. Advantages & Savings VoIP become mature and is technically stable today. The critical point to transport voice data packages real time with a minimum of delay from sender to receiver is controllable now by using quality of service solutions of various manufactorers. The biggest benefit of VoIP phones is found in an universal network not only on infrastructur level (physical layer) but as well on the protocoll level. The physical and logical separation of voice and data networks is gone, resulting in a major cost saving potential. Maintenance of those universal networks can be covered by the same sevice team for all voice and data applications. Space consuming PBX, phone systems and crossconnect racks will go away and be replaced by powering Ethernet switches and servers. As well here a huge cost saving potential can be found. Users comfort of most VoIP phones is same or better than most ISDN phones but the functionality is much higher with VoIP phones. 8. The Future Almost sure the importance of Voice over IP will significantly increase in the future. A little more thrilling is the following idea: If now phones can be used by a universal RJ-45 interface with voice data and power, which other applications might come? Of course the transmission of video data packes of a security or web camera might be a commercial interesting idea if the camera can be fed with sufficient energy using the RJ-45 interface. One step further the notebooks batteries could be charged via the RJ-45 Ethernet connection - as well mobile phones, organizer, PDAs etc -making external power cables sockets needless. In principle each end device with less than 16 Watts power consumption could be connected this way. Halogene spots at your desk could receive the energy over the RJ-45 connector etc. Maybe the RJ-45 has the potential to become the first worldwide standard power connector for all low power consuming devices. Current standardization works on doubling the maximum energy up to 30 Watts which would cover even more devices and applications. 13

14 9. AMPCO Power Converters AMP CO Plus is the most flexible system in the premise cabling world. It uses the sheath sharing option to keep investment costs and the amount of cable used at a minimum. System modules allow you the use of two powered links via one cable: modules at the panel side convert Mode A or B into Mode A which brings to DC power under the AC signal using only two pairs per link. At the outlet the power is extracted again from Mode A to Mode A and B so that your VoIP device can select the prefered mode. One more reason to go for a universal premise cabling system: Each port can be converted from an voice to a data port easiliy. With a dedicated phone network installed in parallel to the data network you have no migration option. The maximum of flexibility and migration option can be used if you choose for a universal premise cabling system which is as flexible as the AMP CO System with exchangeable insert modules. No other system can deliver two powered Ethernet ports via just one cable! 14

15 10. Further Informations For further informations about AMP CO plus and solutions for VoIP please contact your local AMP Netconnect office or visit us at / 15

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