I’m going to give it another read or two, but I think you’re right that software developers are *probably* safe from this.

My only remaining doubt is whether a project like OpenWRT (which makes an operating system for network routers) could be threatened by claim #68.

–Accordingly, the need arises for a LAN to which such portable devices can be connected by means of a wireless or radio link.

Such wireless LANs are known, however, hitherto they have been substantially restricted to low data transmission rates. In order to achieve widespread commercial acceptability, it is necessary to have a relatively high transmission rate and therefore transmit on a relatively high frequency, of the order of 1 GHz or higher. As will be explained hereafter, radio transmission at such high frequencies encounters a collection of unique problems.

One wireless LAN which is commercially available is that sold by Motorola under the trade name ALTAIR. This system operates at approximately 18 GHz, however, the maximum data transmission rate is limited to approximately 3-6 Mbit/s. A useful review of this system and the problems of wireless reception at these frequencies and in “office” environments is contained in “Radio Propagation and Anti-multipath Techniques in the WIN Environment”, James E. Mitzlaff IEEE Network Magazine November 1991 pp. 21-26.

This engineering designer concludes that the inadequate performance, and the large size, expense and power consumption of the hardware needed to adaptively equalize even a 10 Mbit/s data signal are such that the problems of multipath propagation cannot thereby be overcome in Wireless In-Building Network (WIN) systems. Similarly, spread spectrum techniques which might also be used to combat multipath problems consume too much bandwidth (300 MHz for 10 Mbits/s) to be effective. A data rate of 100 Mbit/s utilizing this technology would therefore consume 3 GHz of bandwidth.

Instead, the solution adopted by Motorola and Mitzlaff is a directional antenna system with 6 beams for each antenna resulting in 36 possible transmission paths to be periodically checked by the system processor in order to locate the “best quality” path and “switch” the antennae accordingly. This procedure adds substantial bulk and cost to the system. This procedure is essentially the conversion of a multipath transmission problem into a single path transmission environment by the use of directional antennae. –

So, anyone can use the older 6 beam technique and not worry about infringing this patent.

Furthermore, as long as you don’t modulate the data such that the period of a sub-channel symbol is longer than a predetermined period representative of the time delay of significant ones of non-direct transmission paths, it looks to me like you won’t infringe either.

I suppose there is a small chance that software “contributes” to someones infringement. In all likelyhood, that software would be developed by or contracted for by hardware suppliers.

61. A method for transmitting data in a confined multipath transmission environment at radio frequencies in excess of 10 GHz, said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means, said method comprising the steps of:

modulating said data, by modulation means of said transmission signal processing means, into a plurality of sub-channels comprised of a sequence of data symbols such that the period of a sub-channel symbol is longer than a predetermined period representative of the time delay of significant ones of non-direct transmission paths; and

transmitting, by said antenna means, said sub-channel symbols at said radio frequencies in excess of 10 GHz.

62. A method as claimed in claim 61, comprising the further step of providing data reliability enhancement to said data in advance of said modulation step.

63. A method as claimed in claim 62, wherein said data reliability enhancement is Forward Error Correction.

64. A method as claimed in claim 63, comprising the further step of interleaving blocks of said input data between the steps of providing data reliability enhancement monitoring and step of modulation.

65. A method as claimed in claim 64, wherein said blocks of input data are bits.

66. A method as claimed in claim 61, wherein said step of modulation is multi-level amplitude and/or phase modulation (mQAM).

67. A method as claimed in claim 66, wherein said mQAM modulation is one of: multi-level amplitude phase shift keying (mASK), permutation modulation, binary phase shift keying (BPSK), multi-level phase shift keying (mPSK) and multi-level amplitude phase keying (mAPK).

68. A method for transmitting data in a confined multipath transmission environment of radio frequencies, said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means, said method comprising the steps of:

applying data reliability enhancement to said data;

interleaving blocks of said enhanced data;

modulating said data, by modulation means of said transmission signal processing means, into a plurality of sub-channels comprised of a sequence of data symbols such that the period of a sub-channel symbol is longer than a predetermined period representative of significant ones of non-direct transmission paths; and

transmitting, by said antenna means, said sub-channel symbols.

69. A method as claimed in claim 68, wherein said data reliability enhancement is Forward Error Correction.

70. A method as claimed in claim 69, wherein said blocks of input data are bits.

71. A method as claimed in claim 68, wherein said steps of modulation is multi-level amplitude and/or phase modulation (mQAM).

72. A method as claimed in claim 71, wherein said mQAM modulation is one of: multi-level amplitude phase shift keying (mASK), permutation modulation, binary phase shift keying (BPSK), multi-level phase shift keying (mPSK) and multi-level amplitude phase keying (mAPK).