Today, most businesses don’t need any convincing argument about how digital transformation can enhance their agility. The pressing question is how to onboard more and more consumers and how to provide improve service through differentiated offerings.
Given the pivotal role of networks in this era of cloud-powered enterprise, low-cost-per bit is central to creating digital transformation. This imperative is equally applicable from edge of the network to the core, as well the very data center that fuels services.
The need for low-cost-per-bit at the Edge of Network
As applications are quizzing the network, demand for bandwidth is growing. Multi-media transport is a reality today and with that reality is the need for faster response time. Service providers are now baffled with a two-prone challenge: How to improve differentiated service with faster response time and reduce the cost to service. Consumers are demanding better service at relatively cheaper price points for multi-media payload that fuels their need to stay connected, pushing the Petabytes of data to Internet that traverse through various service provider networks. The age-old infrastructure of service provider is simply inadequate to accommodate this demand for more bandwidth. Couple this with the traffic generated by billions of connected devices. Get the picture?
Welcome to the dawn of Zetabyte era! “If each petabyte in a zettabyte were a centimeter it would mean one can reach 12 times higher than world’s tallest tower Burj Khalifa”.[1]
Accommodating this pressing need for bandwidth means opening up the clogged pipe at the wireless and wired edge and web-scale network performance at the Edge of Network. There is no better technology than “Ethernet” and “Fiber” to open up clogged pipe at wired and Wireless Edge.
Unchoking Wireless Edge
You heard it right, wireless network across the globe is getting a shot in the arm as service providers are upgrading the first choking block where your wireless traffic runs down the tower to meet wired pipe. Perhaps you too have experienced this change to some extent while browsing Internet or watching YouTube video, there is no screeching halt or buffering of app in your smartphone. While this experience may be limited to users of certain service providers, work is underway for all tiers of providers to unchoke their wireless edge. It is a dire need of their business.
When your data rides over RF frequency from your cell phone to reach the antenna of your mobile provider, it undergoes digitization at an “analog to digital” conversion device known as RRH (Radio Remote Head). From there, the bitstreams run down the pipe to meet its first transport gateway of packetization known as Baseband Unit or short BBU. Up until this point, the network is known as fronthaul. Please read more in my earlier article to know more about frounthaul at http://www.dhimanchowdhury.com/2018/01/13/hello-world/ .
In early days, constraints of interconnects choked this entry point of your data. However, new technologies made it possible to reshape the architecture of interconnects and moves the bulky pieces of equipment away from the tower base. Fiber is now rising up the tower upto RRH and allowing bigger pipe up to 20GbE to antenna base through a means of interconnect known as CPRI. Compare this to early days of coaxial interconnect that only allowed short distance interconnect and less than 100MBps of transfer rate. In my article about wireless and fiber convergence, I made a case for overhauling RRH with addition of Ethernet. If CPRI is limited to 20GbE bandwidth, having Ethernet at the very base of antenna the pipe could be enormous: 100GbE to 400GbE. IEEE already created an open and free standard to create ethernet transport at fronthaul known as ROE (Radio over Ethernet). While RoE promises the potential for fatter pipe at cheaper cost, it is still in research phase. What possible though is the bandwidth upgrade in the connectivity between BBU and operator’s packet network known as “mobile backhaul”.
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| Figure 1. Typical fronthaul and backhaul Network architecture |
Many operators started to upgrade the pipe between BBU and backhaul aggregation using a device known as cell site router or sometimes referred to as cell site gateway. This creates a fatter pipe from 1GbE to 10GbE for each fronthaul endpoint. Prior to such upgrade many deployments had 10/100Mbps at this level connectivity. Now the 4G fronthaul service can use 1GbE pipe while 5G 10GbE. This is just an example of upgrade underway. The important conduit to this upgrade is whitebox open networking platform. As such cell site router not only endows the benefits of an unlocked system, it innately reduced the cost per bit and improve services.
Unleashing the power of open networking at Wireless Edge
The Cell Site Router (please refer to figure 1) is not a new concept, there are many deployments of it using OEM switches. However, the cost of OEM switches is extremely high. It also poses challenge that inherent of vendor locked system making it difficult for operator to deploy in massive scale. This constraint can be completely eliminated by deploying “Whitebox Cell Site Router” that utilizes state of the art merchant silicon while offering the benefit of low cost per bit and the choice of hardware and software. The TIP (Telecom Infra Project) initiative for open networking infrastructure product to serve telecom service provider has undertaken activities around the same concept known as DCSG (Disaggregated Cell Site Router)[2]. The term “whitebox CSR (Cell Site Router)” and DCSG are synonymous. Central to this concept is separation of hardware and software as in whitebox but applied to Cell Site Router for specific deployments in mobile backhaul. There can be variations of DCSG devices ranging from 12 ports of 1/10GbE to 48 ports of 10GbE with 2 to 6 ports of 100GbE.
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| Figure 2. Whitebox Cell Site Router or DCSG (Disaggregated Cell Site Router) Architecture |
Additionally, the DCSG or Whitebox CSR provides SyncE and PTP (1588) clocking capabilities. It will help synchronize between GPS clock and packetized clocking information retrieved from packet network. Clocking is essential part of mobile backhaul transport. There are varied deployments using DCSG or whitebox CSR ranging from Ring interconnect to CLOS fabric interconnects. For example, the figure below shows typical ring interconnect allowing various RAN (Radio Access Network) configurations in MPLS network. Such configuration allows wider area coverage for various RANs including 5G and migration path from 4G to 5G for operators.
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| Figure 3. Typical Ring topology of interconnect for mobile backhaul. |
For migration path from 4G to 5G, network operator benefits from utilizing same DCSG based network for both 4G and 5G. As shown in figure 3, 5G base station Distributed Unit (DU) [3][4] can be connected to same DCSG where 4G base station is connected. 5G deployment requires a spit of base station in two parts distributed unit (DU) and Central Unit (CU) [3][4] for which DU may reside on or near the tower and CU is placed in 5G core network. The CU is then connected to servers to provide various network functions through NFV (Network Function Virtualization). Please note DU can provide upto 100GbE link and RoE capabilities making it easier to integrate into your packet network. Within the DCSG based MPLS network primary and secondary path can be created easily making fail over faster and reliable. Other variation of this network could be DWDM based long distance interconnect between MPLS mobile backhaul (BMH) Ring and MBH aggregation (please refer figure 3).
Passive Optical Network for Wireless Edge
With the advent of whitebox OLT (Optical Line Terminator), Passive Optical Network (PON) can now be extended to fronthaul. The benefit of such deployment is that same fiber can carry mixed set of traffic allowing fronthaul connection and residential/business fixed line services over the same fiber. As such overall TCO (total cost of ownership) will be drastically reduced.
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| Figure 4. Mixed Traffic PON for MBH and fixed line services. |
In figure 4, a typical example of mixed traffic PON deployment is shown. There can be two types of OLT deployments using whitebox solutions: whitebox OLT device and whitebox Ethernet switch with OLT transceivers.
For the first, OLT functions are realized through virtualized solution known as VOLTHA. In this scenario, mixed traffic from MBH, residential and enterprises are carried over single fiber depending upon split ratio. Typical split ratio is 1:32 meaning 32 ONUs can be connected to single incoming fiber. For the second solution, OLT transceivers can be used with standard whitebox ethernet switch. These OLT transceivers are available in SFP+ form factor making it easier to plug it in a 10GbE SFP+ port socket of the whitebox switch. OLT functions can be virtualized with VOLTHA or it can be implemented in the Ethernet switch itself. IP Infusion, a leader of independent NOS (Network Operating System) for whitebox platform, implements OLT functions through a container within its OcNOS™ software. Third-party OMCI stack that provides OLT functionalities can be integrated within OcNOS container for which Netconf API provides EMS (Element Management System) based configuration and management capabilities including provision of ONUs.
Solutions such as these reduce overall TCO for operators and offers the choices and benefits of open networking. Low-cost-per-bit is essential today for operators to improve service and maximize ROI.
Reference:
1. Cisco, 2016. The Zettabyte Era Officially Begins (How Much is That?). Available at https://blogs.cisco.com/sp/the-zettabyte-era-officially-begins-how-much-is-that
2. Lightwave, 2018. Telecom Infra Project targets disaggregated cell site gateways. Available at https://www.lightwaveonline.com/articles/2018/10/telecom-infra-project-targets-disaggregated-cell-site-gateways.html .
3. Microsemi, 2019. 5G LTE Base stations. Available at https://www.microsemi.com/applications/5g-mobile-infrastructure/5g-lte-base-stations .
4. Techplayon, 2017. 5G NR gNB Logical Architecture and Its Functional Split Options. Available at http://www.techplayon.com/5g-nr-gnb-logical-architecture-functional-split-options/
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