Broadcast and video applications have sought ways to place HD digital video cameras in remote locations without wires or concern for interference. Both 3D filming and HD video have consumed available wireless bandwidth, pushing solutions higher in frequency towards millimeter-wave bands for these applications. Users in motion picture, television, sports, and Electronic News Gathering (ENG) organizations have looked for wireless methods of supporting these applications, with MMW frequencies offering the required bandwidths.

Millimeter Waves Extend Wireless Services, Fig. 3

Because 3D is shot essentially utilizing two cameras that film slightly offset images that are synchronized to create the dimensional effect, two independent HD streams must be transmitted simultaneously.  This immediately doubles the data transmission requirement and presents the challenge of doing so through a delivery system—physical or wireless—that has no latency issues. Fiber-optic cables used for digital 3D/HD applications have suffered latency problems that can affect the synchronization of the two digital streams of data.  To compensate, complex and expensive multiplexers are needed, requiring racks of on-site equipment and a completely nonportable solution. Because of problems with fiber-optic cables, 3D/HD signals are often transferred by means of coaxial cables at distances to 300 m, although often with some sacrifice in resolution and signal quality.

Millimeter-wave frequency bands offer an alternative to fiber-optic and coaxial cables for transferring 3D/HD signals. For example, millimeter-wave radio links developed by Renaissance/HXI (the firm’s GigaLink HD links) transmit uncompressed raw HD/SDI video at 1.485 GB/s.  Available in single- and dual-channel formats, the radio links transmit at distances to 500 m under clear-air conditions. They were developed for use with Sony HDC and HDCU-F950 Digital 4:4:4 CineAlta systems but can interface with any SMPTE 372M or SMPTE 292M compliant production system. Dual-channel versions of these millimeter-wave systems can transport independent video signals from two HD cameras or synchronized HD 3D signals at a combined rate of 2.970 Gb/s. The millimeter-wave systems operate without compression or forward error correction (FEC), to avoid the associated latency issues.

High-Frequency Trading

Millimeter-wave radios offer great promise for high-frequency-trading (HFT) applications, where trades must be executed quickly. These radios can speed connections between data centers and their markets. HFT grew from a Security & Exchange Commission (SEC) decision in 1998 to allow electronic exchanges to compete with the NYSE and other marketplaces. By 2010, HFT was accounting for more than 70% of the trades in US equity markets, and a growing percentage of trades in other countries. HFT is not based on large changes in stock prices but on analyzing large amounts of information to find opportunities for stock trading profits that may have been otherwise overlooked. Large profits can be made by executing millions of smaller transactions each day. HFT practices may involve holding stocks for mere seconds, and will start each day without any holdings.

Millimeter Waves Extend Wireless Services, Fig. 4

HFT can produce profits based on small amounts per transaction, such as a quarter cent per share. According to Tabb Group, a financial markets research and strategic advisory firm, by 2008 traders earned $21 billion in profits from HFT. HFT is successful when teamed with the proper infrastructure, so that trading companies involved in HFT heavily invest in the hardware, software and personnel necessary to gather and analyze momentary changes in market data and then execute based on that data, and latencies must be minimized. Exchanges that have implemented systems for HFT have typically brought down the latency to about 3 ms on average.

Network communications latency is obviously a key concern for an application such as HFT. Contributors to network latency include the time it takes for a packet to travel between one place and another at the speed of light, the medium itself (optical fiber, wireless), and the size of the packet since larger packets take longer to receive and return than smaller ones. Latency can also be affected by the speed of processing through a router or other gateway node, and packets can experience storage and hard-disk access delays at intermediate devices such as switches and bridges.

Physical distances between communications points can affect latency. To reduce latency, trading firms have placed their computers as close as possible to those of the exchange. Of course, fear of terrorism attacks on the NY Stock Exchange have also caused many firms to move their data centers further from Manhattan, increasing the distances between HFT computers and trading systems and sometimes adding microseconds in latency to each round-trip signal transmission. But adding lines, such as fiber-optic cables, in a large city can cause problems, as Pleasant notes: “Running fiber often isn’t practical in an urban environment. To install fiber, you have to disrupt local infrastructure like digging up streets or hanging it on pre-existing structures, which is expensive and time consuming.”

Because of the difficulties in installing high-speed fiber-optic communications lines, many HFT companies are using wireless transmission systems to connect their data centers to the stock exchange. For a sufficiently short distance, a single millimeter-wave link can be used to make a direct connection. When distances are too great for a single link, a series of millimeter-wave links can be used to relay signals. The use of millimeter-wave technology can help an HFT firm to reduce latency in their connections versus fiber-optic links. As Pleasant points out: “Lower latency equals faster trading speeds which equals more money to be made for the end user. In this industry nanoseconds count, so having the lowest latency connections is a big deal.”

Renaissance Electronics and Communications, LLC, 12 Lancaster County Road, Harvard, MA 01451; (978) 772-7774.