蜂窝多路复用器买家指南2014

As part of a project I began for 流媒体 4 years ago, I’m now currently tracking 16 vendors of cellular multiplexers (as well as a handful of channel-bonding and link aggregation technology providers). The number of vendors is up by four from last year and up by 11 since 2010!

That is quite significant growth for any niche in this sector, 分开, 也许, from the online video platform rash that had an outbreak about 5 years ago and promptly disappeared.

Especially notable is that each of the vendors that has entered the market has at least one strong differentiator from the others. 根据我的经验, vendors in these streaming media subgenres can be very catty about the others’ products, but the cellular video multiplexer (cellmux for short) community is generally very mature when you talk about the pros and cons of one particular product over the others in the space. This indicates to me that the vendors are finding that the competition is only helping to grow the market and that the market growth is outpacing the growing number of products and vendors. This, of course, is a healthy thing for everyone, particularly the buyer.

让我们快速浏览一下基本的产品类型, with a few comments about the features that you should be thinking about when making your buying decision. 首先，让我们确保我们了解产品.

Cellmux is a combination of a video encoder and a channel-bonding link aggregator. “那是什么鬼东西??“我听见你在哭.

A link aggregator is a device that can connect multiple Layer 2 network links (for example, ADSL, 以太网, 无线网络, and fiber together and aggregate the bandwidth in such a way that any requests can be load balanced across all of these available connections. 用于网络流量或突发电子邮件等, a link aggregator can effectively allow a group of people using many applications to always find an uncongested route over which they can reliably send and receive their chunk of data.

批判性的, a link aggregator only needs the one device at the customer premises, 并且不需要在网络中远程操作. Each request is load-balanced and sent via the least congested route. 对于突发数据, 这为用户提供了更高的网络可用性, 增加每个用户的带宽比率. 然而, if the highest bandwidth connection is (for example) 1Mbps, then the user who “gets time” on that connection may stream video up to 1Mbps, 但即使有10个以上的1Mbps连接, the fastest video they will be able to stream will still only be 1Mbps.

In order for a consumer to exceed this 1Mbps limit, a secondary stage needs to be added. A remote device located in a hosting center that has (for example) 100Mbps connectivity could work in conjunction with the consumer’s link aggregator to work out how to split chunks of (for example) a 4Mbps stream over several of the link-aggregators’ 1Mbps pipes. It would then coordinate reconstituting these separated chunks of video back into a coherent, 单, 更高比特率流. 这个过程是“多路复用”的一种形式,在这个模型中, 第二层链路通常是不同类型的, 常用的术语是“通道键合”.”

So a channel-bonding link aggregator has two parts -- one in the consumer’s location and one in a well-connected hosting location.

Channel-bonding systems work well and have been around for many years. In 2003, I recall using ISDN channel bonding to combine six 128Kbps links into a 单 768Kbps “pipe” for streaming 512Kbps quality video.

然而, when you move off fixed QoS connections onto 无线网络 and mobile connections, 通道键合容易发生变化. If you set up your video encoder to produce a fixed 512Kbps, 很有可能, 有时, only a few channels will be available -- so the aggregate bandwidth will be insufficient to continue to stream your 512Kbps source stream. 现在, while we are all familiar with adaptive bitrate streaming, typically this is something implemented between the server and the end users’ media players to help to deal with these volatile network conditions of the end users. 大多数制作网络广播的读者都知道, the connection between the origin encoder and the origin server (from where the distribution networks source their signal) is imperative. If your source from the encoder to the origin server is bad, then every user experience is bad (also known as a garbage in, 垃圾, 或GIGO, 流程). 相应的, it is very important that if the mobile encoder is passing through areas of variable signal coverage that the video between the encoder and the server must also be adaptive. 为了确保这一点, there must be some computational communication between the network layer channel bonding link aggregation and the video encoding process.

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