Data center boom comes
Some of the most interesting technological changes are currently under way, such as 100G Ethernet being used in data centers and radio access networks, and the shift towards high-speed fiber-optic Ethernet is driving the need for higher-performance frequency and frequency control products.
As traditional enterprises are rapidly shifting their workloads to public cloud infrastructure, bringing a massive global investment boom to data centers, in addition to the growing demand for low latency, data centers face unique challenges in terms of workloads Processing is spread across multiple compute nodes while most of the data center traffic remains in the data center.Modern data centers are optimizing their network architecture to support distributed virtualization operations by connecting each switch to one another, which Is known as "Hyperscale Computing." One of the foundational technologies that make the ultra-large computing business attractive is high-speed Ethernet, as shown in Figure 1. Data center switches are rapidly moving to 25G, 50G and 100G Ethernet networks to speed data transmission and network efficiency.
Figure 1 Data center switch to 25/50 / 100G Ethernet
Data Sources: Dell'Oro Market Research, Ethernet Switch Update, (1/2017)
The move from 10G to 25/50 / 100G Ethernet is driving data center equipment manufacturers to upgrade switches and access ports to higher speeds, which in turn requires more efficient, lower-jitter timing solutions. Ultra-low jitter frequencies and oscillators are necessary in these applications, as high-frequency noise can cause unacceptably high bit error rates or communication disruptions.Table 1 highlights the typical timing requirements for Ethernet PHYs, switches, and switch fabrics. A safe and reliable way to implement a high-speed Ethernet network is to use ultra-low jitter frequency sources, which provide excellent jitter tolerance for these specifications (Table 1).
Significant increase in data transfer LTE-Advanced into a key technology
As wireless networks move from 4G / LTE to LTE-Advanced and 5G over the next few years, there will be enormous changes in the wireless network, with next-generation wireless networks optimized for mobile data activity, which is expected to grow by 2021 Exabyte 49 per month, seven times more than in 2016. To support this exponential growth in bandwidth needs, wireless networks are redesigning and optimizing data transmission. Radio Access Network (RAN) High-Speed Ethernet The widespread adoption is expected to be a key part of this technological advance.
In the 4G / LTE radio access network, the RF and baseband processing functions performed by the base station are divided into independent remote radio transceiver modules (RRHs) and centralized baseband units (BBUs). As shown in Figure 2, each RRHs are connected to the BBU over a dedicated optical fiber based on the Common Radio Interface (CPRI) protocol, which enables them to be replaced by a connection between a radio transceiver (usually located in a base station tower) and a base station (usually located near the ground) Dedicated Copper and Coax Cables The distributed architecture allows the BBU to be placed in a more convenient location to simplify deployment and maintenance Although more efficient than traditional 3G wireless networks, bandwidth is limited by the CPRI link speed (typically 1 Gbps To 10 Gbps), the network architecture is limited.In addition, the CPRI connection is a point-to-point link and RRHs and BBUs are usually deployed near each other<2km至20km), 这限制了网络部署的灵活性.
Figure 2 4G / LTE wireless access network (CPRI)
As part of the evolution of 5G, the wireless industry is rethinking the base station architecture.The connection between baseband and radio components, known as Fronthaul networks, is a key area for optimization.With the need for higher-bandwidth Fronthaul networks to support high-speed mobile data New LTE features include carrier aggregation and large-scale MIMO In addition, network density and adoption of Small Cell, Pico Cell and Micro Cell will bring additional bandwidth requirements for the front-end network.In order to minimize CAPEX and OPEX, 5G The Cloud-RAN (C-RAN) architecture will be used to apply Centralized Baseband Processing (C-BBU) to multiple RRHs.
New standards for Fronthaul have been developed to support C-RAN evolution. The IEEE1904 Access Network Working Group (ANWG) is developing a new Radio over Ethernet (RoE) standard to support CPRI encapsulation on Ethernet networks The new standard will increase the utilization of Fronthaul networks by aggregating CPRI traffic from multiple RRHs and Small Cells over a single RoE link Another working group, the IEEE 1914.1 Next-Generation Fronthaul Interface (NGFI), is reexamining RF and The first layer of separation between baseband to support more Layer 1 processing at the RRH NGFI enables the Fronthaul interface to move from point-to-point connectivity to multipoint-to-multipoint topologies, thereby increasing network flexibility and enabling Better Coordination Between Base Stations The new 5G Front-Haul CPRI Standard (eCPRI), scheduled to be released in August 2017, details the new functional division of base station functionality and supports CPRI transport over Ethernet.
These new Fronthaul standards create the need for a frequency-agile timing solution that requires support for RRH, Small Cell, Pico Cell's LTE and Ethernet frequencies.These new solutions provide a unified design for hardware design from all frequencies to a single small size IC opportunities.
Another key challenge is accurate timing and synchronization Historically, 3G and LTE-FDD mobile networks have been synchronized by frequency to synchronize all network components to a very accurate and accurate primary reference frequency, which typically comes from the GNSS satellite system (GPS, BeiDou) These systems require frequency accuracy of 50 ppb on the radio interface and 16 ppb on the Backhual network at the base station interface LTE-TDD and LTE-Advanced preserve these frequency accuracy requirements but add The very strict phase synchronization requirements (± 1.5us) are key requirements for implementing new features such as enhanced inter-base interference coordination (eCIC) and coordinated multi-point (CoMP) to maximize signal quality and spectral efficiency. These phase synchronization requirements are expected to be further enhanced by the upcoming 5G standard.
Figure 3 LTE-Advanced Radio Access Network
Figure 5 shows an LTE-Advanced network architecture in which multiple RRHs are connected to a centralized BBU over a packet-based eCPRI network and phase / frequency synchronization is provided by IEEE 1588v2 / SyncE IEEE 1588 / SyncE support timing is implemented on RRH and centralized BBUs And phase synchronization Higher bandwidth The 100GbE network is used to enable Backhual traffic to be communicated from each BBU to the core network.More efficient and flexible timing solutions are now available to simplify frequency generation and distribution in LTE-Advanced applications And synchronization.
Reduce data transmission costs to create new services
Ethernet is widely used in data centers and wireless networks for higher network utilization and lower cost data transmission and to enable new service provider functions and services.In these infrastructure applications, Based Ethernet is driving the demand for more flexible, lower jitter timing solutions. Major timing equipment vendors are meeting this market need through high-performance frequency and oscillators based on innovative architectures to achieve the largest Frequency flexibility and ultra-low jitter.