Double Helix Ch. 22

Gena

My foot lurched sideways, slipping on a patch of the roof where the chimney cast a shadow and moss had coated the shakes. A pair of hands grabbed me before I could fall, one on my arm while the other went to my waist.

"Careful," Nock said, "it's a long way down."

"Yeah," I said, my heart slowly coming back down from my throat. The roof sloped down from here about twenty feet before dropping off into empty space, with the ground two stories below.

"You okay, baby girl?" he asked, his face reflecting his concern.

"Not really," I admitted. "Let's just get this done and get down." I didn't have a fear of heights, but I definitely had a healthy respect for them. Stan had offered to place the antenna, but I had insisted, reminding him that the hardware was my responsibility to assemble and test. Part of me was wishing now that I had taken his offer.

I decided that putting the antenna on the chimney's south side would work just as well as the moss-covered north side, and drilled four neat holes in the bricks, using the bracket Nock held in place as a guide. The antenna itself was a simple affair, a six-foot tall pole whose transmission pattern looked like what you would get if you rotated a narrow triangle around in a circle. Focusing the signal in that way would boost the signal strength by several decibels.

I fastened the antenna to the bracket, clamped the thick ground wire to the chimney's central metal pipe, and played out a bit of coaxial wire from the box that Nock had retrieved from the edge of the roof. The run of wire was already tacked down under the eve and down the side of the house to the first floor.

"What if lightning hits this thing?" Nock asked.

I pointed to the ground wire. "That's what this is for. If a big surge hits, there's an arrestor there that will direct it into the chimney, which is grounded. It might torch the antenna, but all the expensive stuff in the house will be fine." I thought about that for a second. "Probably," I amended.

I screwed down the fittings and worked the rubber seals onto the connectors to protect them from the weather, then used a couple of the little wire clips from a pouch on my tool belt to fix the cable in place. "Okay, that should do it," I said. I tapped the transmit button on my comm. "It's all set, Stan. How's our signal strength?"

"We're checking," Stan said. He came back a few seconds later. "Node 5 is a little low, but it should be enough."

"Great!" I said. "Let me come back down and we'll fire this thing up."

We were in what we called West House, the westernmost of the three farmhouses. It was the one that I lived in and was node 1 on our new network. The main house, what most people called the big house, was node 2. Alice's house, on the other side of the big house, was node 3. Node 4 and 5 were just dumb terminals hooked up to wireless transceivers at a distance of two and three miles from node 1. We had placed them inside abandoned houses to shelter them from the elements and supplied them with solar panels to give them just enough power to operate.

Nock and I made our way carefully down the slope of the roof to the ladder. Well, I moved carefully. With his reflexes, falling was likely not an issue. Hell, even if he did fall, it wouldn't be an issue. I had seen him drop to the ground from a three-story parking garage without injury, after all. I was glad now that he had insisted on coming up here to give me a hand. It made me feel a whole lot safer.

Nock went first down the extension ladder, waiting for me a few steps down. I tried to figure out how I was supposed to mount the ladder from up here, and looked down past Nock without meaning to. The twenty feet to the hard dirt below suddenly look like fifty. I quickly took a step back. I'm not sure it was completely voluntary.

"It's easy," Nock said. "Just grab hold of the side rails in both hands and swing one foot out to put on a rung." I wanted to let him know just how "easy" such an insane move sounded, but I had to get down from here sooner or later. I followed his direction and carefully stepped off the roof, planting my foot on one of the narrow rungs.

"You've got it, little tomato," he said. "Now just transfer your weight to that foot and bring over the other one."

I did as he said, physically shaking as I let the ladder take my weight. I found the rung with my other foot and remembered to breathe. "I'm okay," I said. "I did it."

Nock moved down a step to make room for me to follow. "You know," he said, "you've actually got really nice legs."

I glanced over my shoulder and saw him looking up. "Wait just a damned minute!" I said. "Did you actually insist on coming up here with me for the sole purpose of getting a chance to look up my skirt?"

"No," he said innocently. "That's not the only reason. I mean, that's not the reason." His grin was as big as a canyon.

"Oh, you are such a dog!" I said.

"Never claimed otherwise."

We bantered the rest of the way down the ladder. Of course I wasn't actually offended, but it didn't occur to me until we were nearly to the ground that he had probably said that to distract me from being on a shaky ladder two stories up. That didn't stop me from teasing him mercilessly. When I came off the ladder, he put out his arms to pull me in for a kiss, and I put my palm out. "Nope. You want to stare at my ass, that's all you get to kiss." I brushed past him, heading for the door.

"Well you do have a very kissable ass," he said.

"And you've got a very kickable ass."

He apparently didn't have a good comeback to that, as he came up behind me and swept me from my feet with a growl. I squealed--not entirely an act--and kicked my feet uselessly as he spun me around in a circle. "Put me down!" I demanded.

"Who's going to kick my ass?" he taunted.

"Come on, Nock," I protested. "I want to run this test."

"You must first pay the toll," he intoned in his deep voice.

I sighed dramatically. "Fine."

He set me back on my feet. I crossed my arms and pursed my lips comically, but my posing only lasted until his lips touched mine and I forgot all about the silly game we had been playing and returned the kiss with all my usual enthusiasm. Then he grabbed my butt.

"Hey!" I snapped, and swatted his hand away.

"Oops," he said, "must have slipped."

"That's what you said last time."

"So how about that test you were going to run?"

"I'll get you back later," I said.

I loved the flirting and the teasing. We had been together--dating seems like a terrible description for it when you live only a two minute walk apart--since November. It was the middle of February, almost three months since we had rescued Sasha, and, for better or worse, I was still a virgin.

Yes, you read that right. I would be turning twenty-four soon and had never done the deed. It's not that I was into chastity or anything like that. Well, okay, maybe that was part of it. Mom took me to church, pardon the pun, religiously throughout my childhood. I knew that she disapproved of premarital sex, even if I and all my peers thought it wasn't a big deal. But it was also that I wanted my first time to be with someone I genuinely cared about, someone special, and up until that point in my life, the pickings had been pretty slim.

Nock was pretty damned special. He was the guy most people talked to first when they linked up to the darknet. He was charming, funny, and knew how to make a girl feel like she was the center of his world. On top of that, he has the strength of four men, can see in the dark, and can shoot the wings off a fly from a mile away. Somehow, I had managed to catch his eye, and there was no way in hell I was going to let him slip away.

I went inside, took off the tool belt and got the wire box from Nock, stowing both in the utility room adjacent to the laundry. Then I headed for the tech room. Stan and Stanford were both at their terminals when we walked in. "We're all set," Stan said. "Start her up whenever you're ready."

Though it was placed in a corner of the room, the Samsung computer, a rack-mounted microserver, was the center of our operation. Usually only large businesses owned such devices, due to an expensive annual license that you must purchase to own one legally. Possessing such a computer without that license was class D felony with mandatory jail time. Of course, if I were to try to categorize all of the various ways that we had collectively broken the law up to that point and add up all of the criminal penalties involved, we would probably all be executed at least three times over, then have our corpses sent to prison for a few hundred years. But that was just part of the risk we were taking to try to make the world a better place.

That microserver was hardwired to a commercial wireless router, and it was to this device that my antenna up on the roof fed. The other four nodes had less powerful antennas, but we had tested them to work effectively with each other out to a distance of one mile. Once in mesh topology, node 1 should be able to reach nodes 2, 3, 4 and 5, Node 2 should be able to reach node 1 and 3, Node 3 could reach nodes 1, 2, and 4, and node 4 could reach nodes 1, 3 and 5. That gave our network at minimum two different pathways to hit any other node. For example, for data to reach from node 2 to node 5, data could either go to node 1, then out to 5, or it could go to 3, then 4, then 5. It was even possible for it to go from node 2 to 3, then 1, then 5, if the load on the different nodes was shifting around a lot.

With the mesh network on standby, we were at that moment operating a network that used traditional star topology, with node 1 as the hub. That network would run in parallel with the mesh network on a different frequency band, and allow us to send commands directly to each node. I went to my terminal and opened a command line, typed a command to execute a script and hit Enter. "Okay, I'm commanding our nodes to start discovery," I said. "Connections should start going up. What do we have?"

"I'm seeing handshakes all around," Stanford said, referring to the process of each node verifying the credentials of every other node within its range and adding that node to its list of available destination points. They would then establish encryption key pairs so that each node could transmit securely to the nodes within its range. To allow us to monitor this process, each node would relay its logs of everything that occurred back through the command network. "Looks like each node has acknowledged the other nodes within reach."

"I'm moving on, then," I said. Now came the crucial part. I typed a new command. "I'm initiating the network now." I hit Enter and walked up behind Stan.

"The nodes are propagating," Stan said. Each node was now transmitting the existence and address for the nodes that it could reach to every other node. This would, for example, tell node 4 about the existence of node 2, and vice versa, even though the two of them couldn't directly communicate. "I've got confirmation. Each node has the complete network map."

"Alright," I said. "I think we're ready to try transmitting data."

Stan sent a few packets over the command network to multiple nodes in turn. Node 5 was ordered to send data to node 2. In this case, it chose to send it back through node 1, since that required only one hop to complete. Node 2 then sent to node 4, via node 3. Node 4 sent data to node 1 directly, and Node 1 then hit node 5 directly. All of the data streams were correctly received with no loss, and the nodes seemed to be making good use of the strengths of the topology.

"So far, so good," Stan said. "Let's up the ante."

He sent a new set of directives over the command network, and nodes 2, 3 and 4 began broadcasting a long string of packets nearly simultaneously, targeting nodes 5, 4, and 1, respectively. The load balancing was obviously working, as node 2 used node 1 to jump to 5, node 3 transmitted directly to node 4, and node 4 directly transmitted to node 1, since it could get no greater bandwidth from going through the other nodes. Again, no packets were dropped.

Now we proceeded to the real stress tests, and all five nodes were given instructions to transmit at random intervals to the other nodes on the network. Things held together for a few seconds before they started to break down.

"Crap!" I said, as dropped packets showed up everywhere at once.

"Looks like we're getting collisions," Stan said, "Lots of them."

"Alright, shut it down," I said in a tone of dismay and disgust.

Stan pushed a command and all five nodes immediately stopped transmitting. "Dammit!" I said, smacking my fist against my thigh. I felt Nock's large hand rubbing my back comfortingly.

"Don't worry about it," Stan said. "That wasn't bad for our first test. You just have to figure out where things went wrong with your code or your algorithms and start to patch it."

I went back over to my terminal. I had been working on this network for weeks, pulling twelve and fourteen hour days, and it had crashed and burned in just a few seconds. A log of all of the network activity was waiting for me, a veritable encyclopedia of data to chronicle my failure.

Nock pulled up a chair next to me to sit. He gave my shoulder a squeeze at seeing my hesitation and spoke quietly next to my ear. "Stan didn't seem all that upset. I don't think he was expecting perfection your first time out. You just find the problem and fix it, right?"

I didn't answer, but I opened up the network log file to have a look. The data from all five nodes was jammed in here together in chronological order, showing when each node attempted to transmit along with the outcome of -success- or -failure-, indicating whether or not the receiving node had received recognizable data. All it told me was what I already knew, where the string of nearly unbroken -success- logs had switched to -failure-. The collision avoidance algorithm must have completely broken down, because all five nodes were trying to send data at the same time and almost nothing was actually being received.

I found it, after ten minutes of studying the logs. Stan had wanted to make use of an experimental technique that I had described in my original academic paper. Normally wireless network devices couldn't transmit and receive at the same time, unlike wired network devices. A network that could pull this off was called full duplex. In a wireless network, each node's own transmissions overwhelmed their ability to receive signals from other nodes. It was like trying to hear someone else when you yourself are shouting.

Our network solved this by applying a half-wavelength phase-shifted version of the transmitted signal to the receiver's input signal, canceling out the node's own transmission signal. I had gotten that idea from the concept of negative feedback and wave cancellation, widely used in acoustics. However, early in development, I had hard-coded the phase shift to test the concept's viability, but had neglected to go back and tell the software to set the shift based on the frequency in use. That mistake caused the canceling signal to be far enough out of phase to make the whole mechanism useless.

"That would do it," Stan said. He had come to stand over my shoulder, and I felt my cheeks burning. "Good work finding it so quick. You know what to do to fix it?"

"Oh, uh, yeah, no problem," I said. I adjusted the canceling signal to be dependent on the transmitting signal and recompiled. "I'll have the new code loaded in a minute," I said over one shoulder.

"God, that was embarrassing," I said under my breath when Stan walked away, knowing that Nock would still be able to hear me. It was a newbie mistake, which I had compounded by failing to find in testing.

"It's just a bug," Nock said. "Don't sweat it."

I struggled not to grind my teeth. What he didn't understand was that it was a rather stupid bug, one that neither of the Stans would have been likely to write into their code.

As if reading my thoughts, Nock added, "Just wait until Sam starts picking apart Stanford's encryption and Stan's authentication protocols. That guy is a machine." I smiled at that thought. Tilly had told me a few stories about the hell that the enigmatic hacker had put them through when they were working to set up the dark net. I was suddenly glad that I wasn't in charge of security.

Stan restarted the network test with the revised code. This time, data moved flawlessly back and forth between nodes for the entire run of the test. Theoretically, implementing full duplex doubled the available data rate, and our testing bore this out. We hadn't yet realized the real gains of using mesh topology yet, which would push the performance even higher relative to a standard star network. There were other innovations that we would introduce in later iterations, but this test was a proof of concept to demonstrate that the tech was likely worth pursuing.

Stan clapped me on the back after we shut down the network once more. "Excellent work, Gena," he said. "I know you've been putting in long hours. Why don't you take the afternoon off?"

"She would love to," Nock said, before I could consider refusing. There was still a ton of work to do. My next priority was the beamforming problem, which, if we could get it to work, would make our network faster, project farther and make it more difficult to detect.

Though, I reflected, it would give me a chance to talk to Tilly, and I could run a few of my ideas by her. Give her a couple of minutes and she usually thought of a way to deal with a problem that seemed intractable. Hell, she often thought of solutions to problems that I hadn't even considered yet.

"Yes, she would love to," I echoed, and gave Nock a frown as we walked out. "What do you have planned?"

"Just looking for a little time with my baby girl," he said with conspicuous innocence. "You haven't been to the big house in two days. I wouldn't have known about your rooftop gig this morning if Stan hadn't mentioned it at dinner last night."

"Yeah, I'm sorry," I said. "I've been getting ready for this test for a week and didn't want to take the hour out of my day last night. I was trying to finish a review and QA of every part of my code." I rolled my eyes. "Not that it helped me when it came down to it."

"Still think you've got something to prove, huh? No one is questioning your abilities or commitment. You've earned your place here."

"Easy for you to say," I scoffed. "You can pull a twenty hour day every day and still have some leisure time." Nock just shook his head at that.

The orchard trees were devoid of leaves at this time of year, so we could see the construction vehicles from right outside West House. Two excavators were at work in the area to the north of the big house, though we could only see the top of the cabs and their digging arms.

"Want to see how it's going?" Nock asked, pointing. I nodded.

Coming closer, I spotted my brother standing at the edge of the huge pit being slowly dug into the landscape. I was still getting used to calling him Norm, rather than his actual name, but he had explained to me that he and Nissi used their real names only when intimate. I didn't want to spoil that for them, and the handful of times that I had started to slip, I managed to catch it in time.

Norm had revised his original plan of a single floor of underground apartments once he realized that it would occupy the space of half a football field. Making it two floors basically doubled the depth that they would need to excavate, but the overall movement of earth would be less. Also, it reduced the amount of wiring and plumbing that would be required.

The east side of the pit sloped down in a ramp to roughly where the floor of the top level would be, sixteen feet below the surface. The excavators were at work deepening that pit, moving from east to west. The deepest part of the pit was at the level of the bottom floor, twenty-eight feet down. Bedrock in the Willamette Valley sometimes lay hundreds of feet below the surface, making it terrible for skyscrapers, but ideal for our building project.