DirectBand

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FM station channels RDS vs DirectBand FM-spectrum2.svg
FM station channels

DirectBand was a North American wireless datacast network owned and operated by Microsoft. It used FM radio broadcasts in over 100 cities to constantly transmit data to a variety of devices, including portable GPS devices, wristwatches and home weather stations.

Datacasting is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital terrestrial television, but may also be applied to digital signals on analog TV or radio. It generally does not apply to data which is inherent to the medium, such as PSIP data which defines virtual channels for DTT or direct broadcast satellite systems; or to things like cable modem or satellite modem, which use a completely separate channel for data.

Microsoft U.S.-headquartered technology company

Microsoft Corporation (MS) is an American multinational technology company with headquarters in Redmond, Washington. It develops, manufactures, licenses, supports and sells computer software, consumer electronics, personal computers, and related services. Its best known software products are the Microsoft Windows line of operating systems, the Microsoft Office suite, and the Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface lineup of touchscreen personal computers. As of 2016, it is the world's largest software maker by revenue, and one of the world's most valuable companies. The word "Microsoft" is a portmanteau of "microcomputer" and "software". Microsoft is ranked No. 30 in the 2018 Fortune 500 rankings of the largest United States corporations by total revenue.

Contents

How it works

DirectBand used the 67.65 kHz subcarrier leased by Microsoft from commercial radio broadcasters. This subcarrier delivers about 12 kbit/s (net after ECC) of data per tower, for over 100 MB per day per city. Data included traffic, sports, weather, stocks, news, movie times, calendar appointments, and local time.

A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.

Not like RDS

DirectBand did not use the RDS (Radio Data System) subcarrier. RDS is a different system and has much lower data rate (~730 bit/s after ECC, including framing). Its much narrower subcarrier is primarily used for radio station information and traffic. DirectBand and RDS can co-exist on the same FM station.

Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identification and program information.

Forward acting error correction

Since many DirectBand uses were mobile, and there was no opportunity to request retransmission of a broadcast signal, DirectBand utilized an advanced error-correction strategy that allowed for reconstruction of messages even when sizable portions of the message were lost due to buildings, tunnels or other obstructions of the FM signal. Error correction was 1/2 rate interleaved trellis with time diversity, soft-decision decode. The DirectBand data rate was in excess of 12 kbit/s after ECC.

In telecommunication, trellis modulation is a modulation scheme that transmits information with high efficiency over band-limited channels such as telephone lines. Gottfried Ungerboeck invented trellis modulation while working for IBM in the 1970s, and first described it in a conference paper in 1976. It went largely unnoticed, however, until he published a new, detailed exposition in 1982 that achieved sudden and widespread recognition.

Push network

DirectBand was a push network  new content was delivered every two minutes. Users pre-selected the virtual channels that they were interested in.

Receivers

There were a variety of DirectBand receivers. All used a small (2.794 mm × 2.794 mm × 860 µm) radio receiver. Some designs added an ARM7-based processor.

ARM7 is a group of older 32-bit RISC ARM processor cores licensed by ARM Holdings for microcontroller use. The ARM7 core family consists of ARM700, ARM710, ARM7DI, ARM710a, ARM720T, ARM740T, ARM710T, ARM7TDMI, ARM7TDMI-S, ARM7EJ-S. The ARM7TDMI and ARM7TDMI-S were the most popular cores of the family. Since ARM7 cores were released from 1993 to 2001, they are no longer recommended for new IC designs; instead ARM Cortex-M or ARM Cortex-R cores are preferred.

The initial DirectBand products were a series of data watches. These had mild success, but never met expectations and production of new watches was discontinued in 2008. Recently, several other applications have surfaced, the most visible being the traffic data/local info market, particularly to auto GPS sets for Garmin and Avis. This competes directly with older RDS-based services, which operate at a substantially lower data rate.

Microsoft design

DirectBand is a product of the Smart Personal Objects Technology (SPOT) team at Microsoft. System hardware was designed for Microsoft by SCA Data Systems of Santa Monica, California. [1] MSN Direct is the consumer brand that Microsoft uses for devices that receive content from the DirectBand network.

Smart Personal Objects Technology

The Smart Personal Objects Technology (SPOT) is a discontinued initiative by Microsoft to create intelligent and personal home appliances, consumer electronics, and other objects through new hardware capabilities and software features.

MSN Direct was an FM radio-based digital service which allowed 'SPOT' portable devices to receive information from MSN services. Devices that supported MSN Direct included wristwatches, desktop clocks, in-car GPS satellite navigation units, and even small appliances such as coffee makers. Information available through paid "channels" included weather, horoscopes, stocks, news, sports results and calendar notifications. The service also allowed users to receive short messages from Windows Live Messenger.

FM subcarrier usage

RDS uses a portion of the FM station spectrum immediately above the stereo signal, centered at 57 kHz (the stereo pilot frequency). RDS extends between about 55 and 59 kHz. DirectBand is above RDS, extending from about 59 kHz to 75 kHz.

Shutdown

On October 26, 2009, Microsoft announced that MSN Direct service would end on January 1, 2012. [2]

Although this clearly indicated Microsoft's intent to cease usage of the service, it is not yet known whether the DirectBand technology will be sold to another company, such as one of the hardware licensees of MSN Direct (e.g. Garmin)  or whether the technology will be put in the public domain as an open source technology.

See also

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References

  1. SCA Data website
  2. "MSN Direct service will be available only until January 1, 2012". MSN Direct web site. Archived from the original on 2010-10-09.