Requirement of Synchronous Ethernet aka syncE

From the last two decades Ethernet is becoming the dominant technology in service provider as well as in Telecom domain. Being it’s asynchronous behavior, providers faced lot of issues to integrate it with the existing TDM technologies. TDM mainly works on clock which means synchronization is required among all the nodes.

Now service providers are moving towards the Next Generation Network aka NGN or Packet Converge Network aka PCN. The challenge which they are facing is the clock synchronization between the TDM networks over Ethernet network. By nature Ethernet doesn’t provide any clock mechanism but thanks to synchronous Ethernet aka syncE which helps to make communication possible between TDM to TDM cloud over packet core network.

In synchronous Ethernet frequency is transferred over physical level than using any upper layers. Every syncE network equipment contains an internal clock called Ethernet Equipment Clock aka EEC. By doing this master slave interconnected tree is built and clock is passed from one node to another.  One primary reference clock (PRC) is used which normally serves the clock to the equipments.

One more category of clock is used which is also known as Synchronous Supply Unit (SSU). SSU are mainly required for given three reasons:-

1. Reduce the jitter in clock.
2. Act as a node clock.
3. Serve the clock in case of failure of PRC.

According to ITU-T Rec. 803 standard, maximum depth of EEC could go up to 60 EEC nodes. The hierarchy is shown in depicted picture:-

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Wimax Interfaces Naming Convention

IP network interfaces are called as core interfaces,access interfaces or PE-CE interfaces. But in WIMAX, interfaces are named as depicted belows:-
1. R1 Interface:- This is actual wireless interface which connects Mobile Subscriber to BS(Base Station).
2. R2 Interface:- This is the logical interface with CSN(Core Service Network). In case of Mobile IP.
3. R3 Interface:- Interface between ASN(Access Service Network) and CSN(Core Service Network).All the radius messages are exchanged on this interface.
4. R4 Interface:- This is the logical interface between ASN-Gty(Access Service Network). This interface is used during handovers in romaing.

5. R5 Interface:- This is logical interface between Home CSN(Core Service Network). This is used during roaming scenarios.
6. R6 Interface:- This is the physical or logical interface between BS(Base Station) and ASN-Gty.
7. R7 Interface:- This is logical/physical interface between decision point and enforcement point. Both are the parts of ASN-Gty.
8. R8 Interface:- This is logical interface between BS(Base Station). This is used during handovers from one BS to another.


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Wimax Architecture

Wimax is fully ip network which gives the last mile users to access internet at high speed. Wimax architecture consists of the following components:-
1. MS(Mobile Subscriber) or SS(Subscriber Station)
2. ASN (Access Service Network)
3. CSN (Core or connectivity Service Network)
MS or SS are used by the users to connect the VPN or Internet by using air interface. All the MS or SS connects to the BS(Base Station) and BS further connects to the ASN-Gty.
ASN network consists of Base Stations and ASN-Gty(Access Service Network Gateway). BS are responsible for providing air interface to mobile subscribers to connect VPN or Internet. Apart from this BS manages the subscribers QOS policy enforcements, traffic classification, session managements and handovers during roaming.

ASN-Gty works as LNS(Layer 2 Network Server) server which aggregates all the layer 2 traffic and provides the connectivity to internet. A part from this it manages QOS profiles, keys management, radius client, mobility tunnels with base stations for roaming users. Allocates profile as Simple and Mobile ip communication for SS or MS and becomes foreign agent for them.

CNS consists of AAA, HA, VHR, OSS. It connects to the internet gateway to route the traffic in case of data network. If MS looks for voip calls in that case it also provides the connectivity to PSTN network.

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Why Wimax Not GSM or CDMA?

In legacy GSM network, we usually use GPRS( General Packet Radio System) and then EDGE(Enhanced Data Rates For GSM Evolution). EDGE is the one which provides the highest throughput 384Kb. But with the passage of time more applications are added in the global network like facebook,orkut and media applications like youtube and iptv which demands more bandwidth. But it's not possible to deliver these type of application in the existing GSM network. Parallel there is one more group which is working on CDMA2000 which is able to deliver the bandwidth more than GSM network. But the main problem with CDMA is that no roaming functionality is available.

To increase the throughout and higher data transfer rates for mobile subscriber, Wimax(Worldwide Interoperability for Microwave Access) is the upcoming standard which is being adopted by most of the service providers. The advantage of using Wimax is that no intellectual property rights. Any vendor can use anything according to the standards listed as in Wimax forum. Wimax falls in 4G category which is fully based on packet switched core(IP Core), no more circuit switching. Wimax works on 802.16d(Stationed) and 802.14e(Roaming) standards. Current Wimax revision provides upto 40 Mbps of speed which is almost equivalent to DS3. Wimax is using OFDM(Orthogonal Frequency Division Multiplexing). Wimax is last mile technology and it could be implemented on existing infrastructure.
Reasons for Wimax not GSM or CDMA:-
1. Intellectual Property Rights (IPR) problems with 3G (Qualcomm).
2. Large ecosystem is developing including handset vendors
3. Will go all-IP End to End years ahead of 3G.
4. “open” systems.
5. Fit with the existing infrastructure.
6. Higher ARPU(Average Revenue Per User).


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